Multi-stage thermal management systems and methods

ABSTRACT

A multi-stage thermal management system includes a fluid loop configured to supply a chilled heat transfer fluid to a plurality of thermal loads having different cooling demands. The system includes a plurality of heat rejection components arranged in stages and fluidly coupled to the fluid loop. The plurality of heat rejection components is configured to receive a return heat transfer fluid from the plurality of thermal loads and extract heat from the return heat transfer fluid to generate the chilled heat transfer fluid. A control system is configured to selectively draw the chilled heat transfer fluid from each heat rejection component individually and to direct the chilled heat transfer fluid to the plurality of thermal loads based on the different cooling demands of the plurality of thermal loads to meet each of the different cooling demands via supply of the chilled heat transfer fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of U.S. Provisional Application No. 63/168,552, entitled “MULTI-STAGE THERMAL MANAGEMENT SYSTEMS AND METHODS,” filed Mar. 31, 2021, and U.S. Provisional Application No. 63/270,385, entitled “MULTI-STAGE THERMAL MANAGEMENT SYSTEMS AND METHODS,” filed Oct. 21, 2021, each of which is herein incorporated by reference in its entirety for all purposes.

BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) systems typically operate to control a temperature of a thermal load (e.g., a fluid, device, structure, or space serviced by the HVAC&R system) via circulation of a heat transfer fluid (e.g., water, brine, refrigerant, air, etc.) between and/or across various heat exchange equipment of the HVAC&R system. For example, the HVAC&R system generally includes a compressor or pump configured to circulate a flow of heat transfer fluid along a series of conduits (e.g., pipes) and between heat exchangers of the HVAC&R system. The heat exchangers facilitate transfer of thermal energy between the thermal load, the heat transfer fluid, and a receiving load (e.g., an ambient environment surrounding the HVAC&R system). As such, the HVAC&R system facilitates transfer of thermal energy to or extraction of thermal energy from the thermal load via circulation of the heat transfer fluid through the conduits and between the heat exchangers. In this way, the HVAC&R system may be used to facilitate temperature control of the thermal load. Unfortunately, existing HVAC&R systems may be ill-equipped to facilitate efficient temperature regulation of multiple thermal loads.

SUMMARY

The present disclosure relates to a multi-stage thermal management system that includes a fluid loop configured to supply a chilled heat transfer fluid to a plurality of thermal loads having different cooling demands. The multi-stage thermal management system also includes a plurality of heat rejection components arranged in a plurality of stages, where the plurality of heat rejection components is fluidly coupled to the fluid loop. The plurality of heat rejection components is configured to receive a return heat transfer fluid from the plurality of thermal loads and extract heat from the return heat transfer fluid to generate the chilled heat transfer fluid. The multi-stage thermal management system also includes a control system configured to selectively draw the chilled heat transfer fluid from each heat rejection component of the plurality of heat rejection components individually and to direct the chilled heat transfer fluid to the plurality of thermal loads via the fluid loop based on the different cooling demands of the plurality of thermal loads to meet each of the different cooling demands via supply of the chilled heat transfer fluid.

The present disclosure also relates to a multi-stage thermal management system that includes a fluid loop configured to supply a chilled heat transfer fluid to a plurality of thermal loads having different cooling demands. Each thermal load of the plurality of thermal loads includes a respective heat exchanger configured to reject heat to the chilled heat transfer fluid to produce return heat transfer fluid. The multi-stage thermal management system also includes a plurality of heat rejection components arranged in a plurality of stages, where the plurality of heat rejection components is fluidly coupled to the fluid loop in multiple places. The plurality of heat rejection components is configured to extract thermal energy from the return heat transfer fluid to produce the chilled heat transfer fluid. The multi-stage thermal management system also includes a control system configured to adjust a valve system of the fluid loop to selectively direct a portion of the return heat transfer fluid to a heat rejection component of the plurality of heat rejection components associated with a selected stage of the plurality of stages based on a return temperature of the portion of the return heat transfer fluid.

The present disclosure also relates to a multi-stage thermal management system that includes a fluid loop configured to supply chilled heat transfer fluid to a plurality of heat exchangers. The plurality of heat exchangers is configured to reject heat to the chilled heat transfer fluid to produce and discharge a return heat transfer fluid. The multi-stage thermal management system also includes a plurality of stages of heat rejection components fluidly coupled to the fluid loop, where the plurality of stages of heat rejection components is configured to extract thermal energy from the return heat transfer fluid to generate the chilled heat transfer fluid. The multi-stage thermal management system also includes a control system configured to adjust a valve system of the fluid loop to selectively direct a portion of the return heat transfer fluid to a selected stage of the plurality of stages of heat rejection components based on a return temperature of the portion of the return heat transfer fluid and respective temperatures of chilled heat transfer fluid discharged from the plurality of stages of heat rejection components.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a schematic of an embodiment of a multi-stage thermal management system, in accordance with an aspect of the present disclosure;

FIG. 2 is a schematic of an embodiment of a skid assembly of a multi-stage thermal management system, in accordance with an aspect of the present disclosure;

FIG. 3 is a schematic of an embodiment of a multi-stage thermal management system having multiple skid assemblies, in accordance with an aspect of the present disclosure;

FIG. 4 is a schematic of an embodiment of a multi-stage thermal management system, in accordance with an aspect of the present disclosure;

FIG. 5 is a schematic of an embodiment of a skid assembly of a multi-stage thermal management system, in accordance with an aspect of the present disclosure; and

FIG. 6 is a schematic of an embodiment of a multi-stage thermal management system having multiple skid assemblies, in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

As briefly discussed above, a heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system may be used to thermally regulate a thermal load that is serviced by the HVAC&R system. The thermal load may include a space within a building, home, or other suitable structure (e.g., a data center), a device (e.g., an electronic device, an electromechanical device), and/or another suitable space, component, or assembly for which temperature regulation is desired. The HVAC&R system may facilitate temperature regulation of the thermal load via circulation of a heat transfer fluid between various heat exchange equipment of the HVAC&R system. For example, in some cases, the HVAC&R system may include a vapor compression system (e.g., a chiller system) that transfers thermal energy between the heat transfer fluid (e.g., a refrigerant) and a fluid to be conditioned, such as air, water, or brine. A compressor or pump may be used to direct the fluid to be conditioned to a heat exchanger that is in thermal communication with the thermal load. The heat exchanger may enable transfer of thermal energy between the thermal load and the fluid to be conditioned and, thus, facilitate temperature regulation of the thermal load.

In some embodiments, a facility (e.g., a data center, a manufacturing or processing plant) may include a plurality of thermal loads corresponding to various devices, processes, and/or sub-systems (e.g., immersion tanks) of the facility for which thermal regulation is desired. The thermal loads may each have a cooling demand that corresponds to an operating capacity (e.g., a current operating capacity) of the thermal loads. As such, cooling demands between various thermal loads may vary based on the relative operating capacities of the thermal loads during a given time period. For example, in some embodiments, a cooling demand of a particular thermal load may increase as the operating capacity of the thermal load increases. Conversely, the cooling demand of the thermal load may decrease as the operating capacity of the thermal load decreases. Further, target temperature set-points for certain of the thermal loads may be the same as or different from other thermal loads in a system. As an example, target temperature set-points corresponding to a first subset of the thermal loads may be set at a first value that is greater than or less than target temperature set-points corresponding to a second subset of the thermal loads. As such, an overall cooling demand of the facility may, in some cases, correspond to a sum of the individual cooling demands of the thermal loads, where the thermal loads may include the same or unique target temperature set-points relative to one another. A cooling demand of each thermal load may correspond to the particular target temperature set-point of that thermal load.

Conventional HVAC&R systems may be ill-equipped to enable independent, efficient, temperature regulation of multiple thermal loads based on the operating capacities of the thermal loads and/or based on the target temperature set-points corresponding to the thermal loads. As a result, typical HVAC&R systems may be prone to over-cooling a heat transfer fluid intended for supply to certain thermal loads and/or inadequately cooling the heat transfer fluid intended for supply to other thermal loads. Moreover, conventional HVAC&R systems may be unable to adjust operation of the heat exchange equipment of the HVAC&R system based on the current cooling demands of the thermal loads, as well as based on efficiency parameters that may affect the relative operating costs and/or operating efficiencies the heat exchange equipment. As an example, the efficiency parameters affecting the relative operational efficiencies of the heat exchange equipment may include water costs, electricity costs, a temperature of an ambient environment surrounding the HVAC&R system (e.g., dry bulb temperature, wet bulb temperature), a humidity level of the ambient environment surrounding the HVAC&R system, a capacity loading of the heat exchange equipment, and/or other relevant parameters.

It is presently recognized that enabling independent temperature regulation of the thermal loads of a facility or other system may facilitate increased efficiency of an HVAC&R system utilized to condition the thermal loads. For example, temperature regulation of the thermal loads based on the individual cooling demands (e.g., operating capacities) of the thermal loads and in accordance with the target temperature set-points corresponding to the thermal loads (e.g., which may be indicative of at least a portion of the cooling demands) may enable a reduction in costs associated with operating the HVAC&R system along with an increased ability to recover useful heat energy. Further, it is presently recognized that coordinating operation of the heat exchange equipment of the HVAC&R system based on one or more monitored efficiency parameters may increase an overall operational efficiency of the HVAC&R system.

Accordingly, embodiments of the present disclosure are directed to multi-stage thermal management system (e.g., a hydronic system architecture) for an HVAC&R system that is configured to facilitate independent temperature regulation of each of multiple thermal loads, or subsets of the thermals loads, serviced by the HVAC&R system, as well as to adjust operation of heat exchange equipment of the HVAC&R system based on monitored efficiency parameters of the HVAC&R system. For example, as discussed in detail herein, the multi-stage thermal management system may include a system architecture having various heat exchange equipment arranged in a tiered hierarchy of stages (e.g., a base stage, a first stage, a second stage, etc.). Each stage of heat exchange equipment may be configured to thermally regulate (e.g., reject heat from) the thermal loads serviced by the HVAC&R system. In some embodiments, a common heat transfer fluid (e.g., water) may be circulated through the various stages to enable operation of the HVAC&R system. A relative operating efficiency of each stage may depend upon current values (e.g., real-time values) of the monitored efficiency parameters, as well as the overall cooling demand (e.g., real-time cooling demand) of the thermal loads.

A control system of the multi-stage thermal management system is configured to determine, based on a current cooling demand of the thermal loads and/or based on the efficiency parameters, which stage, or combination of stages, of the heat exchange equipment enables more efficient cooling of the thermal loads while adequately satisfying the cooling demand of the thermal loads. As such, the control system may selectively operate the stage or stages that facilitate more efficient cooling of the thermal loads. In some cases, the control system may stay operation of less efficient stages of the heat exchange equipment and/or heat exchange equipment if and/or when more efficient stages may be utilized to satisfy the current cooling demand of the thermal loads. In this way, the control system may facilitate energy efficient, water efficient, and/or cost efficient cooling of the thermal loads and, thus, increase an overall operational efficiency of the HVAC&R system. As such, the multi-stage thermal management system disclosed herein may overcome the shortcomings of conventional HVAC&R systems set forth above. These and other features will be described in detail below with reference to the drawings.

Turning now to the drawings, FIG. 1 is a schematic of an embodiment of a multi-stage thermal management system 10 (e.g., a hydronic system architecture), also referred to herein as a heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system 12. The HVAC&R system 12 is configured to facilitate temperature regulation of a plurality of thermal loads 14. Each of the thermal loads 14 may be indicative of a device, process, and/or sub-system of a facility or other system serviced by the HVAC&R system 12. That is, each of the thermal loads 14 in the illustrated embodiment may be representative of a device, process, and/or sub-system that may be cooled (e.g., thermally regulated) via operation of the HVAC&R system 12. Although the subsequent discussion describes the HVAC&R system 12 as operating to cool one or more of the thermal loads 14, it should be appreciated that, in other embodiments, the HVAC&R system 12 may be operable in accordance with the techniques discussed herein to facilitate heating of one or more of the thermal loads 14.

In any case, each of the thermal loads 14 may be associated with a corresponding heat exchanger 16 (e.g., a microchannel heat exchanger, a shell and tube heat exchanger, a plate-fin heat exchanger, etc.) that is configured to facilitate heat exchange between the respective thermal load 14 and a heat transfer fluid (e.g., water, glycol, brine, refrigerant) circulated through a fluid loop 18 of the HVAC&R system 12. As discussed in detail herein, the fluid loop 18 includes a plurality of conduits 20 (e.g., pipes) that fluidly couple various heat rejection components 22 (e.g., heat exchange equipment, heat rejection systems) of the HVAC&R system 12 to the heat exchangers 16 and/or to one another. In some embodiments, each of the heat exchangers 16 includes an inlet 24 configured to receive a flow of the heat transfer fluid from the fluid loop 18 and an outlet 26 configured to discharge the flow of the heat transfer fluid from the heat exchanger 16 back to the fluid loop 18. For clarity, in the subsequent discussion, the inlet 24 of a particular heat exchanger 16 may also be referred to herein as an inlet 24 of the thermal load 14 corresponding to that particular heat exchanger 16. Further, the outlet 26 of a particular heat exchanger 16 may also be referred to herein as an outlet 26 of the thermal load 14 corresponding to that particular heat exchanger 16.

In some embodiments, the thermal loads 14 may include one or more low temperature thermal loads 30 (e.g., immersion tanks, liquid to air heat exchangers) and one or more high temperature thermal loads 32 (e.g., immersion tanks, liquid to air heat exchangers). Generally, the HVAC&R system 12 may be configured or operated to cool the low temperature thermal loads 30 to a first temperature value that is less that a second temperature to which the HVAC&R system 12 is configured or operated to cool the high temperature thermal loads 32. That is, the HVAC&R system 12 may operate to, for example, cool the low temperature thermal loads 30 to a temperature within a first temperature range (e.g., a relatively low temperature range) and to cool the high temperature thermal loads 32 to a temperature within a second temperature range (e.g., a relatively high temperature range). Although two low temperature thermal loads 30 and two high temperature thermal loads 32 are shown in the illustrated embodiment of FIG. 1, it should be understood that, in other embodiments, the HVAC&R system 12 may be configured to provide cooling to any suitable quantity of low temperature thermal loads 30 and/or high temperature loads 32.

The HVAC&R system 12 may include a plurality of temperature sensors 34 that are each configured to generate feedback (e.g., data) indicative of a temperature of the heat transfer fluid along various portions of the fluid loop 18 and/or of a temperature of the heat transfer fluid within certain components (e.g., the thermal loads 14, the heat rejection components 22) of the HVAC&R system 12. As discussed in detail herein, feedback acquired by the temperature sensors 34 may facilitate operation of the multi-stage thermal management system 10 in accordance with the techniques discussed herein.

In the illustrated embodiment of FIG. 1, the HVAC&R system 12 includes a first temperature sensor 40 coupled to a conduit 42 of the fluid loop 18 and that is configured to acquire feedback indicative of a temperature of the heat transfer fluid entering the high temperature thermal loads 32. That is, the first temperature sensor 40 may acquire feedback indicative of a temperature of the heat transfer fluid received at the inlets 24 of the high temperature thermal loads 32. In certain embodiments, separate first temperature sensors 40 may be associated with each inlet 24 of the high temperature thermal loads 32 to provide feedback indicative of the temperature of the heat transfer fluid received at each of the individual inlets 24. The HVAC&R system 12 also includes second temperature sensors 44 configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from respective outlets 26 of the high temperature thermal loads 32. The second temperature sensors 44 may be disposed along respective conduits extending between outlets 26 of the high temperature thermal loads 32 and a return conduit 48 of the fluid loop 18. Each of the high temperature thermal loads 32 may also be associated with a respective first modulating valve 50 configured to regulate a flow rate of the heat transfer fluid discharged from the corresponding high temperature thermal load 32 into the return conduit 48. In some embodiments, one or more first pumps 52 may be coupled to the conduit 42 and configured to drive flow of the heat transfer fluid into and through the high temperature thermal loads 32. The first pumps 52 may each include variable speed pumps that are configured to adjust a flow rate of the heat transfer fluid supplied to the high temperature thermal loads 32.

In some embodiments, the HVAC&R system 12 includes a first mixing control valve 60, a second mixing control valve 62, and a third mixing control valve 64 that may be disposed along the conduit 42. The first, second, and third mixing control valves 60, 62, 64 may cooperate to regulate supply of heat transfer fluid from various heat rejection components 22 and/or from the low temperature thermal loads 30 to the first pumps 52. Further, as discussed in detail herein, the HVAC&R system 12 may include a fourth mixing control valve 66, a fifth mixing control valve 68, a sixth mixing control valve 70, and a seventh mixing control valve 72 that are configured to regulate fluid flow along the fluid loop 18 or other fluid loops of the HVAC&R system 12 to facilitate operation of the multi-stage thermal management system 10 in accordance with the techniques discussed herein. Through the following discussion, the first, second, third, fourth, fifth, sixth, and seventh mixing control valves 60, 62, 64, 66, 68, 70, and 72 may be referred to collective as mixing control valves 74. It should be appreciated that, in certain embodiments, relative locations of the mixing control valves 74 along the fluid loop 18 may be different than the locations illustrated in FIG. 1, while still being operable to control fluid flow along the fluid loop 18 in accordance with the techniques discussed herein.

The HVAC&R system 12 may further include a third temperature sensor 78 coupled to a conduit 79 of the fluid loop 18 and configured to acquire feedback indicative of a temperature of the heat transfer fluid entering the low temperature thermal loads 30. That is, the third temperature sensor 78 may acquire feedback indicative of a temperature of the heat transfer fluid received at the inlets 24 of the low temperature thermal loads 30. In certain embodiments, separate third temperature sensors 78 may be associated with each inlet 24 of the low temperature thermal loads 30 to provide feedback indicative of the temperature of the heat transfer fluid received at each of the individual inlets 24. The HVAC&R system 12 includes fourth temperature sensors 80 configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from respective outlets 26 of the low temperature thermal loads 30. The fourth temperature sensors 80 may be disposed along respective conduits extending between outlets 26 of the low temperature thermal loads 30 and the return conduit 48 of the fluid loop 18. Each of the low temperature thermal loads 30 may be associated with a respective second modulating valve 82 that is configured to regulate a flow rate of the heat transfer fluid discharged from the corresponding low temperature thermal load 30 into the return conduit 48. In some embodiments, one or more second pumps 84 may be coupled to the conduit 79 and configured to drive flow of the heat transfer fluid into and through the low temperature thermal loads 30. The second pumps 84 may each include variable speed pumps that are configured to adjust a flow rate of the heat transfer fluid supplied to the low temperature thermal loads 30. In some embodiments, a recirculation conduit 88 may extend from the return conduit 48 (e.g., adjacent or proximate the outlets 26 of the low temperature thermal loads 30) to the conduit 79. The sixth mixing control valve 70 may be configured to regulate flow of heat transfer fluid from the return conduit 48, through the recirculation conduit 88, to the second pumps 84, for example.

The return conduit 48 may direct heat transfer fluid received from the high temperature thermal loads 32 and/or direct heat transfer fluid received from the low temperature thermal loads 30 to the heat rejection components 22. Heat transfer fluid received by any one or combination of the heat rejection components 22 from the high temperature thermal loads 32 and/or the low temperature thermal loads 30 may be referred to herein as “return heat transfer fluid.” That is, “return heat transfer fluid” may be received by one or more of the heat rejections components 22, and the one or more heat rejection components 22 may chill (e.g., reject heat from) the return heat transfer fluid to provide (e.g., output, discharge, generate) a chilled heat transfer fluid. The chilled heat transfer fluid may be subsequently directed (e.g., via one or more conduits) to the heat exchangers 16 of the high temperature thermal loads 32 and/or to the heat exchangers 16 of the load temperature thermal loads 30 in accordance with the techniques discussed herein. The heat rejection components 22 may be arranged in a plurality of stages 90 (e.g., a hierarchical arrangement of stages) that, as discussed in detail herein, may be independently operable and/or operable in groups to facilitate cooling of the thermal loads 14. For example, the stages 90 may include a base stage 92 of the heat rejection components 22, also referred to herein as “Stage 0,” that is fluidly coupled to the return conduit 48 and includes one or more base stage heat rejection components 94. As shown, the base stage 92 is a stage that initially receives flow of the heat transfer fluid from the return conduit 48 (e.g., before the heat transfer fluid is directed to other stages 90). In the illustrated embodiment, the base stage heat rejection components 94 include a heat recovery heat exchanger 96.

The HVAC&R system 12 further includes a first stage 98 of the heat rejection components 22, also referred to herein as “Stage 1,” that is fluidly coupled to the base stage 92 (e.g., via a conduit 100) and includes one or more first stage heat rejection components 102. The first stage 98 is positioned along the fluid loop 18 downstream of the base stage 92 relative to a direction of heat transfer fluid flow through the fluid loop 18. In the illustrated embodiment, the first stage heat rejection components 102 include a dry economizer 104 (e.g., a thermosiphon cooler, a dry cooler, a freeze protected thermosiphon cooler). The HVAC&R system 12 may also include a second stage 106 of the heat rejection components 22, also referred to herein as “Stage 2,” that is fluidly coupled to the first stage 98 (e.g., via a conduit 108) and is positioned along the fluid loop 18 downstream of the first stage 98 relative to a direction of heat transfer fluid flow through the fluid loop 18. The second stage 106 includes one or more second stage heat rejection components 110. In the illustrated embodiment, the second stage heat rejection components 110 include a wet economizer 112 (e.g., a cooling tower 116 and a heat exchanger 118, such as a plate frame heat exchanger, a closed circuit cooling tower, or a membrane evaporative type cooling tower). The HVAC&R system 12 may further include a third stage 120 of the heat rejection components 22, also referred to herein as “Stage 3,” that is fluidly coupled to the second stage 106 (e.g., via a conduit 122) and is positioned along the fluid loop 18 downstream of the second stage 106 relative to a direction of heat transfer fluid flow through the fluid loop 18. The third stage 120 includes one or more third stage heat rejection components 124. In the illustrated embodiments, the third stage heat rejection components 124 include a chiller system 126 (e.g., an air-cooled chiller system, a liquid-cooled or water-cooled chiller system, another mechanical cooling system).

In some embodiments, the conduit 122 may include a first portion 128 and a second portion 130 having a ballast tank 132 fluidly coupled therebetween. As discussed below, the ballast tank 132 may be configured to receive and store chilled heat transfer fluid received from the chiller system 126, for example. The ballast tank 132 may be a portion of the third stage 120 of the HVAC&R system 12. In other embodiments, the ballast tank 132 may be omitted from the HVAC&R system 12. Moreover, in certain embodiments, any one of the base, first, second, and/or third stages 92, 98, 106, 120 may be omitted from the multi-stage thermal management system 10 and/or other stages 90 may be incorporated with the multi-stage thermal management system 10. As discussed in detail below, each of the stages 90 may be operated selectively and independently from other stages 90 of the HVAC&R system 12 to provide heat transfer fluid to one or more of the thermal loads 14.

In the illustrated embodiment of FIG. 1, the HVAC&R system 12 includes a fifth temperature sensor 140 disposed along the conduit 100. The fifth temperature sensor 140 is configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from the base stage 92 and/or of the temperature of the heat transfer fluid entering the first stage 98. The HVAC&R system 12 also includes a sixth temperature sensor 142 disposed along the conduit 108. The sixth temperature sensor 142 is configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from the first stage 98 and/or of the temperature of the heat transfer fluid entering the second stage 106. The HVAC&R system 12 further includes a seventh temperature sensor 144 disposed along the first portion 128 of the conduit 122. The seventh temperature sensor 144 is configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from the second stage 106 and/or of the temperature of the heat transfer fluid entering the third stage 120 (e.g., entering the ballast tank 132). The HVAC&R system 12 includes an eighth temperature sensor 146 disposed along the second portion 130 of the conduit 122. The eighth temperature sensor 146 is configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from the ballast tank 132 (e.g., in embodiments of the HVAC&R system 12 including the ballast tank 132) and entering the chiller system 126. In some embodiments, one or more third pumps 150 are disposed along the conduit 122 and are configured to drive flow of the heat transfer fluid from the ballast tank 132 to the chiller system 126. The HVAC&R system 12 also includes a ninth temperature sensor 151 that is configured to provide feedback indicative of a temperature of the heat transfer fluid discharged from the chiller system 126.

The cooling tower 116 and the heat exchanger 118 of the second stage 106 may form a portion of an auxiliary cooling loop 152. One or more fourth pumps 154 may be disposed along the auxiliary cooling loop 152 to direct a cooling fluid (e.g., water) through the heat exchanger 118 and to spray nozzles 157 of the cooling tower 116. As one of skill in the art will appreciate, the cooling tower 116 facilitates removal of thermal energy from the cooling fluid and accumulation of chilled cooling fluid within a basin 156 of the cooling tower 116. Although the cooling tower 116 is shown as an open loop cooling tower 116 in the illustrated embodiment of FIG. 1, it should be appreciated that, in other embodiments, the cooling tower 116 may be a closed loop cooling tower or a membrane cooling tower. The fourth pumps 154 draw the cooling fluid from the basin 156 and direct the cooling fluid back toward the heat exchanger 118. The heat exchanger 118 may include separate flow paths corresponding to the fluid loop 18 and the auxiliary cooling loop 152. As such, the heat exchanger 118 facilitates heat transfer between the heat transfer fluid of the fluid loop 18 and the cooling fluid (e.g., water) of the auxiliary cooling loop 152 without mixing of the fluids.

A fluid source 160 (e.g., a water supply) may be fluidly coupled to the auxiliary cooling loop 152. The fluid source 160 may be configured to replenish cooling fluid in the auxiliary cooling loop 152 that may be lost due to evaporation of cooling fluid in the cooling tower 116. In some embodiments, the auxiliary cooling loop 152 includes a tenth temperature sensor 162 configured to provide feedback indicative of a temperature of the cooling fluid discharged from the heat exchanger 118 and/or directed to the cooling tower 116 and may include an eleventh temperature sensor 164 configured to provide feedback indicative of a temperature of the cooling fluid discharged from the basin 156 and/or directed to the heat exchanger 118.

In embodiments of the HVAC&R system 12 where the chiller system 126 is a liquid-cooled chiller, the chiller system 126 may include a chiller condenser cooling loop 170, and the chiller system 126 may facilitate heat exchange between the fluid loop 18 and the chiller condenser cooling loop 170. In some embodiments, the chiller condenser cooling loop 170 may be fluidly coupled to the auxiliary cooling loop 152. As such, the chiller cooling loop 170 and the auxiliary cooling loop 152 may circulate a common cooling fluid. The seventh mixing control valve 72 may be configured to regulate flow of the cooling fluid between the chiller cooling loop 170 and the auxiliary cooling loop 152. In some embodiments, the chiller cooling loop 170 includes a twelfth temperature sensor 172 configured to provide feedback indicative of a temperature of the cooling fluid discharged from the auxiliary cooling loop 152 and directed toward the chiller system 126. In certain embodiments, the chiller cooling loop 170 may include one or more fifth pumps 174 configured to drive flow of cooling fluid along the chiller condenser cooling loop 170 and between the chiller system 126 and the auxiliary cooling loop 152, for example.

In some embodiments, the HVAC&R system 12 includes a local controller 180, or a plurality of local controllers 180, that may be communicatively coupled to some of or all of the heat rejection components 22 and/or other devices of the HVAC&R system 12 (e.g., the chiller system 126, the mixing control valves 74, the temperature sensors 34, the pumps 52, 84, 150, 154, and/or 174, etc.). In certain embodiments, the HVAC&R system 12 includes a server 182 (e.g., one or more remote servers) that is communicatively coupled to the local controller 180 via a network 184 and a cloud 186 (e.g., a network interface enabling access to one or more remote servers, virtual machines, etc., for storage, computing, communication, or other functionality). The network 184 and the cloud 186, collectively referred to herein as a cloud network, may enable the server 182 to receive sensor feedback (e.g., as acquired by the temperature sensors 34 and/or other sensors of the HVAC&R system 12) and to monitor and/or control operation of certain of the heat rejection components 22 and/or other devices of the HVAC&R system 12 (e.g., based on the received sensor feedback).

For example, the server 182 may send a control output (e.g., a control signal) to the local controller 180 via the cloud network, and the local controller 180 may adjust operation of one of the heat rejection components 22 based on the control output. In other embodiments, the server 182 may be configured to communicate directly with the heat rejection components 22 (e.g., via the cloud network). In this way, the server 182 may adjust operation of the heat rejection components 22 without input from the local controller 180. In further embodiments, the local controller 180 may be configured to monitor and/or adjust operation of the heat rejection components 22 without input from the server 182. In such embodiments, the server 182 and the cloud network may be omitted from the HVAC&R system 12. Indeed, as one of skill in the art will appreciate, various computing and control systems are envisioned and may be implemented to enable control of the HVAC&R system 12 in accordance with the techniques discussed herein. It should be understood that the local controller(s) 180, the server 182, and/or additional controllers of the HVAC&R system 12 may form a control system 200 of the multi-stage thermal management system 10. The control system 200 may control the multi-stage thermal management system 10 and components thereof in accordance with the disclosed techniques. That is, the control system 200 may control the multi-stage thermal management system 10 via utilization of any one or combination of the local controller(s) 180, the server 182, and/or additional controllers of the HVAC&R system 12.

In any case, as shown in the illustrated embodiment of FIG. 1, the local controller 180 and the server 182 may each include communication circuitry 220, one or more processors 222, and one or more memory devices 224. The processors 222 may include microprocessors, which may execute software for analyzing the sensor feedback, for controlling the heat rejection components 22 and/or any other suitable components of the HVAC&R system 12, and/or for otherwise executing the control schemes described herein. The processors 222 may include multiple microprocessors, one or more “general-purpose” microprocessors, one or more special-purpose microprocessors, one or more application specific integrated circuits (ASICS), and/or one or more programmable logic controllers (PLCs), or some combination thereof. For example, the processors 222 may include one or more reduced instruction set (RISC) processors. The memory devices 224 may include volatile memory, such as random access memory (RAM), and/or nonvolatile memory, such as read-only memory (ROM). The memory devices 224 may store information, such as control software (e.g., compressor and/or pump control algorithms, valve control algorithms), look up tables, configuration data, communication protocols, etc.

For example, the memory devices 224 may store processor-executable instructions including firmware or software for the processors 222 execute, such as instructions for controlling any of the aforementioned components of the HVAC&R system 12. In some embodiments, the memory devices 224 are tangible, non-transitory, machine-readable media that may store machine-readable instructions for the processors 222 to execute. The memory devices 224 may include ROM, flash memory, hard drives, any other suitable optical, magnetic, or solid-state storage media, or a combination thereof. The communication circuitry 220 may facilitate communication between the server 182, the local controller 180, and/or the heat rejection components 22 via suitable communication channels (e.g., wired and/or wireless connections).

In the illustrated embodiment, the control system 200 includes a user interface 226 that may be communicatively coupled to the local controller 180, to the server 182, or both, via the cloud 186 and/or a wired connection. The user interface 226 may include a portable computing system (e.g., laptop, cellular device, other mobile device) or other suitable system that enables an operator to view, modify, and/or control processes or operations of the HVAC&R system 12. Particularly, the user interface 226 may enable the operator to remotely monitor operational parameters of the HVAC&R system 12, to modify control schemes used to operate the HVAC&R system 12, and/or to adjust operation of the individual components of the HVAC&R system 12.

In some embodiments, the control system 200 may be configured to set (e.g., based on user input received at the user interface 226) a first inlet temperature set-point for the high temperature thermal loads 32, respective first outlet temperature set-points of the high temperature thermal loads 32, or both. For clarity, an inlet temperature set-point of a thermal load 14 may be indicative of a desired temperature value of the heat transfer fluid entering the corresponding inlet 24 of the thermal load 14. Moreover, an outlet temperature set-point of a thermal load 14 may be indicative of a desired temperature value for the heat transfer fluid discharged from a corresponding outlet 26 of the thermal load 14. Further, in certain embodiments, the control system 200 may be configured to set (e.g., based on user input received at the user interface 226) a second inlet temperature set-point for the low temperature thermal loads 30, respective second outlet temperature set-points of the low temperature thermal loads 30, or both.

The first inlet temperature set-points (e.g., target temperature set-points) and the first outlet temperature set-points (e.g., target temperature set-points) of the high temperature thermal loads 32 may be referred to hereinafter as “HT inlet set-points” and “HT outlet set-points,” respectively. Further, the second inlet temperature set-points (e.g., target temperature set-points) and the second outlet temperature set-points (e.g., target temperature set-points) of the low temperature thermal loads 30 may be referred to hereinafter as “LT inlet set-points” and “LT outlet set-points,” respectively.

In some embodiments, the control system 200 may be configured to adjust operation of the HVAC&R system 12 to provide heat transfer fluid to the high temperature thermal loads 32 at a temperature that is substantially equal to the HT inlet set-point. The control system 200 may also adjust operation of the HVAC&R system 12 to cause a temperature of the heat transfer fluid discharged from each high temperature thermal load 32 to have a temperature that is substantially equal to the corresponding HT outlet set-points. As discussed below, in other embodiments, the control system 200 may disregard the temperature of the heat transfer fluid supplied to the high temperature thermal loads 32 and control the HVAC&R system 12 to cause a temperature of the heat transfer fluid discharged from each high temperature thermal load 32 to have a temperature that is substantially equal to the corresponding HT outlet set-point of the high temperature thermal load 32.

Moreover, the control system 200 may be configured to adjust operation of the HVAC&R system 12 to provide heat transfer fluid to the low temperature thermal loads 30 at a temperature that is substantially equal to the LT inlet set-point of and to cause a temperature of the heat transfer fluid discharged from each low temperature thermal load 30 to have a temperature that is substantially equal to the corresponding LT outlet set-point. As discussed below, in other embodiments, the control system 200 may disregard the temperature of the heat transfer fluid supplied to the low temperature thermal loads 30 and may control the HVAC&R system 12 to cause a temperature of the heat transfer fluid discharged from each low temperature thermal load 30 to have a temperature that is substantially equal to the corresponding LT outlet set-point of the low temperature thermal load 30.

As used herein, discussion relating to a value or parameter (e.g., a temperature value) being “substantially equal” to another value or parameter (e.g., a target or set-point temperature value) may refer to the value being with a threshold percentage of (e.g., within 5 percent of) the corresponding set-point or target value. Moreover, as used herein, operating the HVAC&R system 12 to supply heat transfer fluid to the thermal loads 14 at temperatures that are substantially equal to the corresponding inlet temperature set-points of the thermal loads 14 and/or operating the HVAC&R system 12 to achieve the corresponding outlet temperature set-points of the thermal loads 14 will be referred to as satisfying a demand (e.g., a cooling demand) of the thermal loads 14.

The control system 200 may selectively and/or individually operate one or more stages 90 of the heat rejection components 22 based on a relative operating efficiency of the one or more stages 90 to adequately satisfy the demand of the thermal loads 14. For example, in some embodiments, the operating efficiency of each of the stages 90 may depend on the particular heat rejection components 22 included in the stages 90 and/or may depend on one or more efficiency parameters that may influence a corresponding efficiency of the heat rejection components 22 included in the stages 90. In some embodiments, the efficiency of a particular heat rejection component 22 may be characterized by a ratio correlating an operating cost and/or an energy consumption of the heat rejection component 22 per a unit of time (e.g., 1 hour, 1 day) to a quantity of energy (e.g., in Joules) removed from the heat transfer fluid in that unit of time by the heat rejection component 22.

As a non-liming example, in certain embodiments, the first stage 98 may include the dry economizer 104 (e.g., a thermosiphon cooler) that is configured to facilitate cooling of the heat transfer fluid in the fluid loop 18 via transfer of thermal energy from the heat transfer fluid to ambient environmental air surrounding the HVAC&R system 12. As such, an overall operational efficiency of the dry economizer 104 may be based on efficiency parameters such as a current cost of electrical energy (e.g., which may be used to operate fans and/or pumps of the dry economizer 104), the cost of the estimated water saved by higher stages, a temperature of the ambient air (e.g., a dry bulb temperature, a wet bulb temperature), and/or a relative humidity of the ambient air.

As another example, in certain embodiments, the second stage 106 may include the wet economizer 112 (e.g., the cooling tower 116) that is configured to facilitate cooling of the heat transfer fluid in the fluid loop 18 via transfer of thermal energy from the heat transfer fluid to the ambient environmental air surrounding the HVAC&R system 12 via an intermediate cooling fluid (e.g., water). As such, an overall operational efficiency of the wet economizer 112 may be based on efficiency parameters such as a current cost of electrical energy (e.g., which may be used to operate fans and/or pumps of the wet economizer 112), a current cost of water used to replenish fluid in the auxiliary cooling loop 152 (e.g., a cost associated with obtaining water from the fluid source 160, including possible sewer charges for cooling tower blowdown, and water treatment charges), a temperature of ambient air (e.g., a dry bulb temperature, a wet bulb temperature), and/or a relative humidity of the ambient air. It should be appreciated that, in certain embodiments, the first stage 98 and the second stage 106 may form a portion of a single product or component (e.g., a skid assembly). For example, the first stage 98 and the second stage 106 may be part of an adiabatic fluid cooler that can selectively operate the first stage 98 (e.g., for dry cooling), the second stage 106 (e.g., for evaporative cooling), or both.

Still further, as discussed above, the third stage 120 may include the chiller system 126 that is configured to facilitate cooling of the heat transfer fluid via transfer of thermal energy from the heat transfer fluid in the fluid loop 18 to the ambient environment (e.g., in cases of the chiller system 126 being an air-cooled chiller) or to the chiller cooling loop 170 (e.g., in cases of the chiller system 126 being a liquid-cooled chiller). As such, an overall operational efficiency of the chiller system 126 may be based on efficiency parameters such as a current cost of electrical energy (e.g., which may be used to operate a compressor of the chiller system 126), a current cost of water (e.g., a cost associated with obtaining water from the auxiliary cooling loop 152), a temperature of ambient air (e.g., a dry bulb temperature, a wet bulb temperature), and/or a relative humidity of the ambient air. Additionally or alternatively, it should be understood that a variety of other efficiency parameters may affect overall operational efficiencies of any of the stages 90 of the multi-stage thermal management system 10 in addition to the factors discussed above. Each of these additional efficiency parameters may be monitored and analyzed by the control system 200 in accordance with the techniques discussed herein.

Generally, operation of the base stage 92 may be more cost and/or energy efficient for cooling of the heat transfer fluid than operation of the first stage 98, operation of the first stage 98 may be more cost and/or energy efficient for cooling the heat transfer fluid than operation of the second stage 106, and operation of the second stage 106 may be more cost and/or energy efficient for cooling of the heat transfer fluid than operation of the third stage 120. As discussed in detail below, when adjusting operation of the HVAC&R system 12 to satisfy the demand of the thermal loads 14, the control system 200 may therefore generally prioritize operation of the base stage 92 over operation of the first stage 98, prioritize operation of the first stage 98 over operation of the second stage 106, and prioritize operation of the second stage 106 over operation of the third stage 120 in order to satisfy the demand of the thermal loads 14. However, it should be understood that, in certain cases, deviations of real-time values of the efficiency parameters discussed above may influence operational efficiencies of each of the stages 90 relative to one another. Accordingly, the control system 200 may operate any suitable combination of the stages 90 to satisfy the demand of the thermal loads 14 while also enhancing an overall operational efficiency of the HVAC&R system 12. That is, the control system 200 may selectively activate, deactivate, or otherwise adjust operation of one or more of the stages 90 based on one or more of the efficiency parameters and/or the cooling demands of the thermal loads 14 (e.g., the low temperature thermal loads 30, the high temperature thermal loads 32). It should be appreciated that the mixing control valves 74 and/or other suitable valves of the multi-stage thermal management system 10 may be adjustable (e.g., based on instructions received from the control system 200) to direct heat transfer fluid from any particular one or combination of the stages 90 to the heat exchangers 16 of the low temperature thermal loads 30, the heat exchangers 16 of the high temperature thermal loads 32, or both. In this way, the control system 200 may selectively and/or individually draw heat transfer fluid from any one or combination of the stages 90 and direct the heat transfer fluid to the heat exchangers 16 (e.g., based on one or more of the efficiency parameters and/or the cooling demands of the thermal loads 14) in a manner that enhances an overall operational efficiency of the multi-stage thermal management system 10. As an example, the control system 200 may adjust the mixing control valves 74 and/or other components of the multi-stage thermal management system 10 to draw heat transfer fluid from the base stage 92 and direct the extracted heat transfer fluid to the high temperature thermal loads 32, and may adjust the mixing control valves 74 and/or other components of the multi-stage thermal management system 10 to draw heat transfer fluid from the third stage 120 and direct the extracted heat transfer fluid to the low temperature thermal loads 30. Additionally or alternatively, the control system 200 may adjust the mixing control valves 74 to selectively blend (e.g., mix) heat transfer fluid extracted from a combination of the stages 90 and direct the blended heat transfer fluid to the low and/or high temperature thermal loads 30, 32.

In some embodiments, the control system 200 may be configured to receive feedback indicative of the efficiency parameters corresponding to one or more of the stages 90 from suitable sensors (e.g., temperature sensors, humidity sensors) and/or from an online source or remote server (e.g., a weather forecast service, an electrical energy provider, a water provider). For example, the control system 200 may be communicatively coupled to ambient sensors 240 (e.g., dry bulb temperature sensors, wet bulb temperature sensors, humidity sensors) that are configured to provide the control system 200 with feedback indicative of the temperature and/or humidity of the ambient air surrounding the HVAC&R system 12. Additionally or alternatively, the control system 200 may be coupled to an external source 242 (e.g., an online source, a computing device of a service provider) that is configured to provide the control system 200 with feedback indicative of, for example, a current cost of water and/or a current cost of electricity (e.g., a real-time water cost, a real-time electricity cost). The control system 200 may utilize efficiency control algorithms to calculate, based on the efficiency parameters, a relative operational efficiency of some of or all of the stages 90 in real-time or on a predetermined time interval (e.g., hourly, daily, weekly, monthly). The control system 200 may utilize the calculated operational efficiencies of the stages 90 (e.g., relative to other stages 90) to control the HVAC&R system 12 in accordance with the techniques discussed herein. For example, as discussed below, the control system 200 may be configured to activate or deactivate particular stages 90 based on the relative operational efficiencies of the stages 90 and based on the current demand of the thermal loads 14 to increase an overall operational efficiency of the HVAC&R system 12 (e.g., as compared to conventional HVAC&R systems that do not utilize the multi-stage thermal management system 10 discussed herein).

For example, during operation of the HVAC&R system 12, the control system 200 may operate the heat recovery heat exchanger 96 of the base stage 92 to cool a flow of the heat transfer fluid received at an inlet of the heat recovery heat exchanger 96. Particularly, the heat recovery heat exchanger 96 may be configured to transfer thermal energy from the heat transfer fluid entering the heat recovery heat exchanger 96 to a heat recovery load 244 (e.g., a heating coil). As such, the heat recovery heat exchanger 96 may decrease a temperature of the heat transfer fluid as the heat transfer fluid flows in a downstream direction through the heat recovery heat exchanger 96.

The HT inlet set-point for the high temperature thermal loads 32 may be set to a value that is greater than the LT inlet set-point for the low temperature thermal loads 30. The control system 200 may monitor the temperature of the heat transfer fluid discharging from the heat recovery heat exchanger 96, also referred to herein as a heat recovery outlet temperature, via the feedback provided by the fifth temperature sensor 140. In some embodiments, the control system 200 may adjust a capacity of the heat recovery heat exchanger 96 to cause the heat recovery outlet temperature to approach and/or reach the LT inlet set-point for the low temperature thermal loads 30. The control system 200 may increase the capacity of the heat recovery heat exchanger 96 by, for example, increasing a flow rate of fluid circulated from the heat recovery load 244 to the heat recovery heat exchanger 96 (e.g., via operation of a pump 246). Conversely, the control system 200 may decrease the capacity of the heat recovery heat exchanger 96 by, for example, decreasing a flow rate of fluid circulated from the heat recovery load 244 to the heat recovery heat exchanger 96 (e.g., via operation of the pump 246).

Upon determining (e.g., upon lapse of a predetermined operational time period of the HVAC&R system 12) that the heat recovery outlet temperature is substantially equal to the LT inlet set-point of the low temperature thermal loads 30, the control system 200 may maintain the first stage 98, the second stage 106, and the third stage 120 in an inactive state or may deactivate the first stage 98, the second stage 106, and the third stage 120. Moreover, the control system 200 may adjust the mixing control valves 74 to direct heat transfer fluid discharged from the heat recovery heat exchanger 96 to the low temperature thermal loads 30. In some embodiments, the fluid loop 18 may be configured in a manner that enables the control system 200 to adjust valves (e.g., the mixing control valves 74) of the fluid loop 18 such that the heat transfer fluid discharged from the heat recovery heat exchanger 96 is directed to the low temperature thermal loads 30 by bypassing the first, second, and third stages 98, 106, and 120 while these stages 90 are inactive. In other embodiments, the control system 200 may direct the heat transfer fluid discharged from the heat recovery heat exchanger 96 through the inactive stages 90 and to the low temperature thermal loads 30. As such, the control system 200 may supply heat transfer fluid to the low temperature thermal loads 30 at the LT inlet set-point via operation of the base stage 92 and without operating the first, second, and third stages 98, 106, and 120.

The control system 200 may adjust the third mixing control valve 64 to direct a portion of the heat transfer fluid discharged from the heat recovery heat exchanger 96 along a conduit 251 to the high temperature thermal loads 32. If the heat recovery outlet temperature is less than the HT inlet set-point of the high temperature thermal loads 32, the control system 200 may adjust the second mixing control valve 62 to direct a portion of the heat transfer fluid (e.g., warmed heat transfer fluid) discharged from the low temperature thermal loads 30 into the conduit 42 and toward the first pumps 52 (e.g., via conduit 258). The heat transfer fluid discharged from the low temperature thermal loads 30 may have a temperature that is greater (e.g., warmer) than the heat recovery outlet temperature of the heat recovery heat exchanger 96. As such, the control system 200 may utilize the second and third mixing control valves 62, 64 to selectively mix heat transfer fluid received from the heat recovery heat exchanger 96 and from the low temperature thermal loads 30 to achieve a flow of heat transfer fluid at the inlets 24 of the high temperature thermals loads 32 that has a temperature that is substantially equal to the HT inlet set-point of the high temperature thermal loads 32.

Upon determining that the heat recovery heat exchanger 96 is operating at an upper capacity limit (e.g., a threshold capacity) and that the heat recovery outlet temperature is still above the LT inlet set-point of the low temperature thermal loads 30, the control system 200 may activate, for example, the first stage 98 of heat rejection components 22, while maintaining the second stage 106 and the third stage 120 in an inactive state. Moreover, the control system 200 may adjust one or more of the mixing control valves 74 (e.g., the third mixing control valve 64, the fifth mixing control valve 68) to direct heat transfer fluid discharged from the base stage 92 into the first stage 98 and to direct heat transfer fluid discharged from the first stage 98 to the low temperature thermal loads 30.

The control system 200 may monitor the temperature of the heat transfer fluid discharged from the first stage 98 (e.g., from the dry economizer 104), also referred to herein as a first stage outlet temperature, via the feedback provided by the sixth temperature sensor 142. The control system 200 may adjust a capacity of the first stage 98 to cause the first stage outlet temperature to approach or reach the LT inlet set-point for the low temperature thermal loads 30. The control system 200 may increase the capacity of the first stage 98 by, for example, increasing a fan speed of fans 250 of the dry economizer 104 (e.g., by increasing a fan speed of a thermosiphon cooler). Conversely, the control system 200 may decrease the capacity of the first stage 98 by, for example, decreasing the fan speed of the fans 250. If the cooling capacities of the base stage 92 and the first stage 98 are suitable to achieve the LT inlet set-point (e.g., upon lapse of a predetermined operational time period), the control system 200 may operate the HVAC&R system 12 to supply the heat transfer fluid from the first stage 98 to the low temperature thermal loads 30 at the LT inlet set-point.

In some embodiments, the fluid loop 18 may be configured in a manner that enables the control system 200 to adjust valves (e.g., the mixing control valves 74) of the fluid loop 18 such that the heat transfer fluid discharged from the first stage 98 is directed to the low temperature thermal loads 30 by bypassing the second and third stages 106 and 120 while these stages 90 are inactive. As such, the control system 200 may supply heat transfer fluid to the low temperature thermal loads 30 at the LT inlet set-point via operation of the base stage 92 and the first stage 98 and without operating the second stage 106 and the third stage 120.

The control system 200 may adjust the first, second, and/or third mixing control valves 74 to direct a portion of the heat transfer fluid discharged from the first stage 98 along the conduit 42 to the high temperature thermal loads 32. If the first stage outlet temperature is less than the HT inlet set-point of the high temperature thermal loads 32, the control system 200 may adjust the second mixing control valve 62 to direct a portion of the heat transfer fluid discharged from the low temperature thermal loads 30 along the conduit 258, into the conduit 42, and toward the first pumps 52. The heat transfer fluid discharged from the low temperature thermal loads 30 may have a temperature that is greater than the first stage outlet temperature. As such, the control system 200 may utilize the first and second mixing control valves 60, 62 to selectively mix heat transfer fluid received from the second and third stages 106, 120 and from the low temperature thermal loads 30 to achieve a flow of heat transfer fluid at the inlets 24 of the high temperature thermal loads 32 that has a temperature substantially equal to the HT inlet set-point of the high temperature thermal loads 32. In some embodiments, the control system 200 may operate the second mixing control valve 62 to enable flow of heat transfer fluid from the conduit 258 to the conduit 42 once the first mixing control valve 60 reaches a threshold position (e.g., after a port 259 of the first mixing control valve 60 reaches a fully open position).

If a temperature of the heat transfer fluid received at the high temperature thermal loads 32 is still less than the HT inlet set-point when the second mixing control valve 62 is positioned to enable full flow from the conduit 258 to the conduit 42 (e.g., through a port 261 of the second mixing control valve 62), the control system 200 may adjust the third mixing control valve 64 to direct a portion of the heat transfer fluid discharged from the base stage 92 into the conduit 42. The heat transfer fluid discharged from the base stage 92 may have a temperature that is greater than the temperature of the heat transfer fluid discharged from the low temperature thermal loads 30. As such, the control system 200 may utilize the third mixing control valve 64 to selectively mix heat transfer fluid received from the base stage 92 with the remaining heat transfer fluid in the conduit 42 to achieve a flow of heat transfer fluid at the inlets 24 of the high temperature thermal loads 32 that is substantially equal to the HT inlet set-point of the high temperature thermal loads 32. In some embodiments, the control system 200 may operate the third mixing control valve 64 to enable flow of heat transfer fluid from the conduit 251 to the conduit 42 once the second mixing control valve 62 reaches a threshold position (e.g., after the port 261 of the second mixing control valve 62 reaches a fully open position).

Upon determining that the base stage 92 and the first stage 98 (e.g., the dry economizer 104) are operating at upper capacity limits (e.g., threshold capacities) and the first stage outlet temperature is still above the LT inlet set-point of the low temperature thermal loads 30, the control system 200 may activate, for example, the second stage 106 of heat rejection components 22, while maintaining the third stage 120 in an inactive state. Moreover, the control system 200 may adjust the mixing control valves 74 to direct heat transfer fluid discharged from the first stage 98 toward the second stage 106 and to direct heat transfer fluid discharged from the second stage 106 toward the low temperature thermal loads 30.

The control system 200 may monitor the temperature of the heat transfer fluid discharged from the second stage 106 (e.g., from the wet economizer 112), also referred to herein as a second stage outlet temperature, via the feedback provided by the seventh temperature sensor 144. The control system 200 may adjust a capacity of the second stage 106 to cause the second stage outlet temperature to approach or reach the LT inlet set-point for the low temperature thermal loads 30. The control system 200 may increase the capacity of the second stage 106 by, for example, increasing a fan speed of fans 260 of the wet economizer 112 and/or by increasing a flow rate of fluid circulation through the auxiliary cooling loop 152 (e.g., via a signal or command sent to the pumps 154). Conversely, the control system 200 may decrease the capacity of the second stage 106 by, for example, decreasing the fan speed of the fans 260 and/or decreasing the flow rate of fluid circulation through the auxiliary cooling loop 152 (e.g., via a signal or command sent to the pumps 154). If capacities of the base stage 92, the first stage 98, and the second stage 106 are suitable to achieve the LT inlet set-point (e.g., upon lapse of a predetermined operational time period), the control system 200 may operate the HVAC&R system 12 to supply the heat transfer fluid from the second stage 106 to the low temperature thermal loads 30 at the LT inlet set-point.

In some embodiments, the fluid loop 18 may be configured in a manner that enables the control system 200 to adjust valves (e.g., the mixing control valves 74) of the fluid loop 18 such that the heat transfer fluid discharged from the second stage 106 is directed to the low temperature thermal loads 30 by bypassing the third stage 120 while this stage 90 is inactive. As such, the control system 200 may supply heat transfer fluid to the low temperature thermal loads 30 at the LT inlet set-point via operation of the base stage 92, the first stage 98, and the second stage 106 and without operating the third stage 120.

During operation of the base stage 92, the first stage 98, and the second stage 106, the control system 200 may adjust the first, second, third, and/or fourth mixing control valves 60, 62, 64, 66 to direct heat transfer fluid to the high temperature thermal loads 32 at a temperature that is substantially equal to the HT inlet set-point of the high temperature thermal loads 32. In particular, the control system 200 may adjust the first, second, third, and/or fourth mixing control valves 60, 62, 64, 66 to mix heat transfer fluid from the base stage 92, the first stage 98, the second stage 106 and/or the low temperature thermal loads 30 to achieve the HT inlet set-point at the high temperature thermal loads 32.

Upon determining that the base stage 92, the first stage 98, and the second stage 106 are operating at upper capacity limits (e.g., threshold capacities) and the second stage outlet temperature is still above the LT inlet set-point of the low temperature thermal loads 30 (e.g., upon lapse of a predetermined operational time period), the control system 200 may activate the third stage 120 of heat rejection components 22. Moreover, the control system 200 may adjust the mixing control valves 74 to direct heat transfer fluid discharged from the second stage 106 toward the third stage 120 and to direct heat transfer fluid discharged from the third stage 120 toward the low temperature thermal loads 30. The control system 200 may monitor the temperature of the heat transfer fluid discharged from the third stage 120 (e.g., discharged from the chiller system 126), also referred to herein as a third stage outlet temperature, via the feedback provided by the ninth temperature sensor 151. The control system 200 may adjust a capacity of the third stage 120 to cause the third stage outlet temperature to approach or reach the LT inlet set-point for the low temperature thermal loads 30. The control system 200 may increase the capacity of the third stage 120 by, for example, increasing a speed of a compressor of the chiller system 126 and/or by adjusting a variable geometry diffuser (VGD) of the compressor. Conversely, the control system 200 may decrease the capacity of the third stage 120 by, for example, decreasing a speed of a compressor of the chiller system 126 and/or by adjusting the VGD of the compressor. In this way, the control system 200 may supply heat transfer fluid to the low temperature thermal loads 30 at the LT inlet set-point via operation of the base stage 92, the first stage 98, the second stage 106, and the third stage 120.

During operation of the base stage 92, the first stage 98, the second stage 106, and the third stage 120, the control system 200 may adjust the first, second, third, fourth and/or fifth mixing control valves 60, 62, 64, 66, 68 to direct heat transfer fluid to the high temperature thermal loads 32 at a temperature that is substantially equal to the HT inlet set-point of the high temperature thermal loads 32. In particular, the control system 200 may adjust the first, second, third, fourth, and/or fifth mixing control valves 60, 62, 64, 66, 68 to mix heat transfer fluid from the base stage 92, the first stage 98, the second stage 106, the third stage 120 and/or the low temperature thermal loads 30 to achieve the HT inlet set-point at the high temperature thermal loads 32. It should be understood that the control system 200 may operate the mixing control valves 74 and/or other valves of the HVAC&R system 12 (e.g., based on the different cooling demands of the low and high temperature thermal loads 30, 32 and/or based on the efficiency parameters) to selectively direct chilled heat transfer fluid from any of the stages 90 to any of the heat exchangers 16 of the low temperature thermal loads 30 and/or any of the heat exchangers 16 of the high temperature thermal loads 32. As a non-limiting example, the control system 200 may operate the mixing control valves 74 to direct chilled heat transfer fluid from the first stage 98 to the heat exchangers 16 of the high temperature thermal loads 32 and to direct chilled heat transfer fluid from the second stage 106 to the heat exchangers 16 of the low temperature thermal loads 30.

In some embodiments, the chiller system 126 may include a minimum operating capacity below which the chiller system 126 may be unable to operate. In some cases, even during operation of the chiller system 126 at the minimum operating capacity, the third stage outlet temperature may fall below the LT set-point of the low temperature thermal loads 30. In such cases, the control system 200 may adjust the fifth mixing control valve 68 to cause warmer heat transfer fluid discharged from the second stage 106 to enter the conduit 79 and mix with the heat transfer fluid discharged from the chiller system 126, while causing at least a portion of the heat transfer fluid discharged from the chiller system 126 to flow into the ballast tank 132. In this way, the control system 200 may increase an overall temperature of the heat transfer fluid directed through the conduit 79 toward the low temperature thermal loads 30 to achieve the LT inlet set-point of the low temperature thermal loads 30. Moreover, adjustment of the fifth mixing control valve 68 may enable the ballast tank 132 to accumulate heat transfer fluid having a temperature that is less that the LT inlet set-point of the low temperature thermal loads 30.

In some embodiments, upon determining (e.g., based on feedback from a sensor) that the ballast tank 132 reaches a low temperature state, the control system 200 may temporarily deactivate the chiller system 126. Upon deactivation of the chiller system 126, the control system 200 may operate to provide heat transfer fluid to the low temperature thermal loads 30 by drawing (e.g., via the second pumps 84) the chilled heat transfer fluid from the ballast tank 132. For example, the control system 200 may operate the fifth mixing control valve 68 and the second pumps 84 to supply heat transfer fluid to the low temperature thermal loads 30 at the LT inlet set-point using heat transfer fluid extracted from the ballast tank 132 and/or heat transfer fluid received from the second stage 106. The control system 200 may be configured to reactivate the chiller system 126 upon receiving an indication (e.g., from a sensor) that the temperature of the heat transfer fluid in the ballast tank 132 reaches a threshold level.

In some embodiments, the control system 200 may adjust the sixth mixing control valve 70 to direct a portion of the heat transfer fluid discharged from the low temperature thermal loads 30 into the recirculation conduit 88 and back to the second pumps 84. As such, the control system 200 may recirculate heated heat transfer fluid (e.g., warmed heat transfer fluid) discharged from the low temperature thermal loads 30 back into the conduit 79 to increase a temperature of the heat transfer fluid supplied to the low temperature thermal loads 30 (e.g., when a temperature of the heat transfer fluid received at the low temperature thermal loads 30 is less than the LT inlet set-point).

In some embodiments, the control system 200 may be configured to adjust the seventh mixing control valve 72 to regulate a temperature of the chiller condenser cooling fluid entering the chiller system 126 (e.g., via the chiller cooling loop 170). For example, in certain embodiments, a condenser 270 of the chiller system 126 may receive a flow of cooling fluid from the fifth pump 174 of the chiller cooling loop 170. The condenser 270 may heat the cooling fluid and discharge a flow of heated cooling fluid into a conduit 272 and toward the seventh mixing control valve 72. A temperature of the cooling fluid circulating through the auxiliary cooling loop 152 (e.g., of the second stage 106) may be less than a temperature of the cooling fluid received from the condenser 270 (e.g., via the chiller cooling loop 170). As such, the control system 200 may adjust the seventh mixing control valve 72 to selectively mix cooling fluid received from the condenser 270 and cooling fluid received from the auxiliary cooling loop 152 to direct a flow of mixed cooling fluid back toward the fifth pump 174. In this way, the control system 200 may utilize the seventh mixing control valve 72 to adjust a temperature of the cooling fluid directed to the condenser 270 of the chiller system 126.

As generally discussed above, the heat exchanger 118 may include a first flow path 280 configured to receive a flow of heat transfer fluid from the fluid loop 18 and a second flow path 282 configured to receive a flow of cooling fluid from the auxiliary cooling loop 152. In some embodiments, the control system 200 may be configured to monitor a temperature differential across the first flow path 280 of the heat exchanger 118 based on feedback received from the sixth temperature sensor 142 and the seventh temperature sensor 144. Further, the control system 200 may be configured to monitor a temperature differential across the second flow path 282 based on feedback received from the tenth temperature sensor 162 and the eleventh temperature sensor 164. In some embodiments, the control system 200 may be configured to adjust operation of components of the auxiliary cooling loop 152 to cause the temperature differential across the second flow path 282 to be substantially equal to the temperature differential across the first flow path 280. As an example, the control system 200 may be configured to adjust an operational speed of the fourth pump 154 to achieve a temperature differential across the second flow path 282 that is substantially equal to the temperature differential across the first flow path 280. In this manner, the control system 200 may reduce the pumping energy of the fourth pump 154.

As discussed above, in some embodiments, the control system 200 may be configured to regulate heat transfer fluid outlet temperatures of the high temperature thermal loads 32 and/or heat transfer fluid outlet temperatures of the low temperature thermal loads 30 to substantially achieve respective outlet temperature set-points of the thermal loads 14. The control system 200 may be configured regulate the outlet temperature of a particular thermal load 14 via adjustment of the modulating valve 50 or 82 associated with that thermal load 14. For example, to increase the heat transfer fluid outlet temperature of a particular thermal load 14, the control system 200 may instruct the modulating valve 50 or 82 associated with the thermal load 14 to transition toward a closed position to reduce a flow rate of fluid flow across the modulating valve 50 or 82 and, thus, increase heat absorption of the heat transfer fluid in the heat exchanger 16 of the corresponding thermal load 14 per unit mass of the heat transfer fluid directed through the thermal load 14. Conversely, to decrease the heat transfer fluid outlet temperature of a particular thermal load 14, the control system 200 may instruct the modulating valve 50 or 82 associated with that particular thermal load 14 to transition toward an open position to increase a flow rate of fluid flow across the modulating valve 50 or 82 and, thus, decrease heat absorption of the heat transfer fluid in the heat exchanger 16 of the corresponding thermal load 14 per unit mass of the heat transfer fluid directed through the thermal load 14. As such, the control system 200 may adjust the modulating valves 50 and/or 82 to achieve the respective outlet temperature set-points of the thermal loads 14.

In some embodiments, the control system 200 may be configured to regulate an operating speed of the first pumps 52 such that at least one of the modulating valves 50 associated with the high temperature thermal loads 32 has a degree of opening that is approximately 95 percent of a total degree of opening of the modulating valve 50, while still achieving the desired outlet temperature set-points of the high temperature thermal loads 32. Similarly, the control system 200 may be configured to regulate an operating speed of the second pumps 84 such that at least one of the modulating valves 82 associated with the low temperature thermal loads 30 has a degree of opening that is approximately 95 percent of a total degree of opening of the modulating valve 82, while still achieving the desired outlet temperature set-points of the low temperature thermal loads 30. In this manner, the control system 200 may reduce or substantially mitigate efficiency losses in the HVAC&R system 12 that may result due to excess pressure differential across the high and low temperature thermal loads 30, 32 and/or due to increased operation of the pumps 52, 84. Additionally, a temperature of the heat transfer fluid directed through the return conduit 48 may be increased, thereby increasing an amount of heat recovery available to the heat recovery load 244 via the base stage 92 and increasing the efficiency at which heat can be rejected in the first, second, and third stages, 98, 106, and 120, respectively.

In some embodiments, the control system 200 may be configured to control the HVAC&R system 12 to achieve the outlet temperature set-points of the thermal loads 14 without regard to the inlet temperature of the heat transfer fluid supplied to the thermal loads 14. In such embodiments, the control system 200 may operate the multi-stage thermal management system 10 in accordance with the aforementioned techniques, but may activate an additional one of the stages 90 once the first or second pumps 52, 84 reaches or exceeds a threshold operating speed.

In some embodiments, certain components of the multi-stage thermal management system 10 may be positioned on one or more skid assemblies. To better illustrate and to facilitate the following discussion, FIG. 2 is a schematic of an embodiment of the multi-stage thermal management system 10 in which a portion 298 of the multi-stage thermal management system 10 is positioned on a skid assembly 300. Particularly, in the illustrated embodiment, at least a portion of the fluid loop 18 is positioned on (e.g., coupled to) the skid assembly 300. The skid assembly 300 includes a plurality of flanges 302 that facilitate fluid coupling of the portion of the fluid loop 18 disposed on the skid assembly 300 and components of the multi-stage thermal management system 10 that may not be supported by the skid assembly 300. For example, the fluid loop 18 may include a first set of flanges 302 that facilitate fluid coupling of the fluid loop 18 of the skid assembly 300 and the base stage 92, a second set of flanges 302 that facilitate fluid coupling of the fluid loop 18 of the skid assembly 300 and the first stage 98, a third set of flanges 302 that facilitate fluid coupling of the fluid loop 18 of the skid assembly 300 and the second stage 106, and so forth. Moreover, the skid assembly 300 may include flanges 302 that facilitate coupling of the thermal loads 14 to the fluid loop 18 on the skid assembly 300. In this manner, the base, first, second, and/or third stages 92, 98, 106, and/or 120 of the multi-stage thermal management system 10 may be positioned remotely from the skid assembly 300. As a non-limiting example, the skid assembly 300 may be positioned within an interior of a building or other structure, while any one or combination of the stages 90 may be positioned on a roof of the building, in a basement of the building, or at another suitable location. Moreover, the thermal loads 14 may be positioned remotely from the skid assembly 300.

In certain embodiments, the skid assembly 300 may be configured to enable implementation of embodiments of the disclosed multi-stage thermal management system 10 in various facilitates that include additional or fewer stages 90 than the stages 90 shown in the illustrated embodiment of FIG. 2. For example, in some embodiments, a particular facility may not include the first stage 98. In such embodiments, end caps (e.g., plugs) may be coupled to the flanges 302 associated with the first stage 98 in FIG. 2. Additionally or alternatively, valves of the skid assembly 300 associated with the first stage 98 may be transitioned to closed positions to block fluid flow to the flanges 302 associated with the first stage 98. In any case, the control system 200 may operate the multi-stage thermal management system 10 in accordance with the techniques discussed above, irrespectively of the particular stages 90 included in the multi-stage thermal management system 10. As such, it should be understood that the control system 200 may be configured to operate embodiments of the multi-stage thermal management system 10 having any suitable number and/or combination of stages 90. In certain embodiments, the fluid loop 18 on the skid assembly 300 may include valves 310 that are communicatively coupled to the control system 200. The control system 200 may be configured to actuate the valves 310 to enable flow of heat transfer fluid to one or more stages 90 or to enable heat transfer fluid in the fluid loop 18 to bypass one or more stages 90.

FIG. 3 is a schematic of an embodiment of the multi-stage thermal management system 10 that includes multiple skid assemblies 320. In particular, the multi-stage thermal management system 10 includes a first skid 322, a second skid 324, and a third skid 326. In the illustrated embodiment, the first skid 322 supports the chiller system 126, the second skid 324 supports the first and second pumps 52, 84, the mixing control valves 74, and the first stage 98, and the third skid 326 support the high temperature thermal loads 32 and the low temperature thermal loads 30 with associated modulating valves 50, 82. It should be appreciated that, in other embodiments, the multi-stage thermal management system 10 may include any other suitable quantity of skid assemblies 320. Moreover, each of the skid assemblies 320 may include additional components or fewer components of the multi-stage thermal management system 10 than those shown in the illustrated embodiment of FIG. 3.

FIG. 4 is a schematic of an embodiment of the multi-stage thermal management system 10 that includes a valve system 400 configured to direct flow of the heat transfer fluid between various components of the HVAC&R system 12, such as between the thermal loads 14 and the heat rejection components 22. For example, as discussed in detail herein, the valve system 400 may include a first distribution valve 402, a second distribution valve 404, a third distribution valve 406, and a fourth distribution valve 408 that may regulate (e.g., enable, block, throttle, adjust, etc.) flow of the heat transfer fluid toward the heat rejection components 22 and/or toward other components of the HVAC&R system 12. The first, second, third, and fourth distribution valves 402, 404, 406, and 408 may be collectively referred to herein as distribution valves 410 and may each be communicatively coupled to the control system 200 in accordance with the techniques discussed above. In some embodiments, the mixing control valves 74, the modulating valves 50, and/or the modulating valves 82 may also form at least a portion of the valve system 400. In the illustrated embodiment, the multi-stage thermal management system 10 includes a first supporting temperature sensor 412, an additional first supporting temperature sensor 414, a fifth supporting temperature sensor 416, a sixth supporting temperature sensor 418, a seventh supporting temperature sensor 420, and a thirteenth temperature sensor 422, which may each be communicatively coupled to the control system 200 and configured to provide the control system 200 with feedback (e.g., data) indicative of a temperature of the heat transfer fluid along corresponding sections of the fluid loop 18, as discussed below. For conciseness, some of or all of the temperature sensors included in the multi-stage thermal management system 10 may be referred to herein collectively as temperature sensors 426.

In the illustrated embodiment of FIG. 4, a low temperature outlet conduit 428 may fluidly couple the outlets 26 of the low temperature thermal loads 30 to the second mixing control valve 62 and to a distribution conduit 430. The distribution conduit 430 may extend between the return conduit 48 and the sixth mixing control valve 70 to fluidly couple the return conduit 48 to the conduit 79. A flow sensor 432 (e.g. a mechanical flow sensor, an ultrasonic flow sensor, and electromagnetic flow sensor) may be fluidly coupled between the low temperature outlet conduit 428 and the distribution conduit 430 and may be configured to provide the control system 200 with feedback indicative of a flow rate of the heat transfer fluid from the low temperature outlet conduit 428 to the distribution conduit 430.

In some embodiments, the control system 200 may operate the valve system 400 and/or other components of the multi-stage thermal management system 10 based on feedback acquired from the temperature sensors 426, for example, to increase a temperature of the heat transfer fluid directed through the return conduit 48 and/or to maintain the temperature of the heat transfer fluid in the return conduit 48 at a desired (e.g., elevated) value. In this manner, the control system 200 may increase the amount of heat recovery available to the heat recovery load 244 via the base stage 92 (e.g., via the heat recovery heat exchanger 96). That is, by operating the multi-stage thermal management system 10 to increase the temperature of the heat transfer fluid directed through the return conduit 48 and/or to maintain the temperature of the heat transfer fluid in the return conduit 48 at an elevated level, the control system 200 may increase the efficiency at which heat can be rejected (e.g., recovered) during operation of the base stage 92, as well as during operation of the first, second, and/or third stages, 98, 106, and 120.

As discussed above, in some embodiments, the control system 200 may be configured to adjust operation of the HVAC&R system 12 to provide heat transfer fluid to each of the high temperature thermal loads 32 at a temperature that is substantially equal to the corresponding HT inlet set-point and to cause a temperature of the heat transfer fluid discharged from each of the high temperature thermal load 32 to have a temperature that is substantially equal to the corresponding HT outlet set-point. For example, the control system 200 may operate the multi-stage thermal management system 10 to direct heat transfer fluid from the base stage 92 and/or the first stage 98 to the high temperature thermal loads 32 via the conduit 42. The control system 200 may evaluate feedback from the sixth supporting temperature sensor 418 to determine whether the temperature of the heat transfer fluid discharged from the first stage 98 (e.g., the first stage outlet temperature) is within a threshold range of the HT inlet set-point of the high temperature thermal loads 32. Upon a determination that the first stage outlet temperature is greater than the HT inlet set-point (e.g., by a threshold value), the control system 200 may operate the valve system 400 to reduce a temperature of the heat transfer fluid received by the high temperature thermal loads 32 to cause the temperature of the heat transfer fluid received at the inlets 24 of the high temperature thermal loads 32 to approach the HT inlet set-point.

For example, the control system 200 may evaluate feedback from one or more of the fourth temperature sensors 80, and/or from a fourteenth temperature sensor 450 disposed along the low temperature outlet conduit 428, to determine a temperature of the heat transfer fluid discharged by the low temperature thermal loads 30. A temperature of the heat transfer fluid in the low temperature outlet conduit 428 may be referred to herein as the LT-load outlet temperature. Upon a determination that the LT-load outlet temperature is less than the HT inlet set-point, the control system 200 may modulate the second mixing control valve 62 to direct heat transfer fluid from the low temperature outlet conduit 428 into the conduit 42 and toward the high temperature thermal loads 32. To this end, the control system 200 may mix (e.g., in the conduit 42) heat transfer fluid received from the first stage 98 and heat transfer fluid received from the low temperature outlet conduit 428 to reduce a temperature of the heat transfer fluid received at the high temperature thermal loads 32. The control system 200 may monitor a temperature of the mixed heat transfer fluid directed toward the high temperature thermal loads 32 via feedback received from the additional first supporting temperature sensor 414, which may be fluidly coupled to the conduit 42 between the second mixing control valve 62 and the third mixing control valve 64, to determine a difference between the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 and the HT inlet set-point. Upon a determination that the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 is still above the HT inlet set-point (e.g., after lapse of a delay time), the control system 200 may modulate the second mixing control valve 62 to increase a flow rate of heat transfer fluid from the low temperature outlet conduit 428 by the conduit 42 and directed toward the high temperature thermal loads 32. The control system 200 may gradually or incrementally adjust the second mixing control valve 62 to continue to increase the flow rate of the heat transfer fluid from the low temperature outlet conduit 428 directed to the high temperature thermal loads 32 until the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 is substantially equal to (e.g., within a threshold range of) the HT inlet set-point or until the flow sensor 432 indicates that substantially no flow of heat transfer fluid is directed into the distribution conduit 430 as bypass flow (e.g., all or substantially all heat transfer fluid discharged by the low temperature thermal loads 30 is directed to the conduit 42).

Upon a determination that substantially all of the heat transfer fluid from the low temperature outlet conduit 428 is directed into the conduit 42 and toward the high temperature thermal loads 32 (e.g., based on feedback from the flow sensor 432 indicating that substantially no fluid flow from the low temperature outlet conduit 428 is directed to the distribution conduit 430), and that the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 is still above the HT inlet set-point, the control system 200 may operate the first mixing control valve 60 and/or the fourth mixing control valve 66 to direct heat transfer fluid from the second stage 106 to the conduit 42 to provide additional cooled heat transfer fluid to the high temperature thermal loads 32. That is, the control system 200 may effectuate mixing of heat transfer fluid received from the second stage 106 with heat transfer fluid in the conduit 42 to further reduce a temperature of the heat transfer fluid directed toward the high temperature thermal loads 32, such that the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 approaches the HT inlet set-point. For example, the control system 200 may gradually or incrementally adjust the first mixing control valve 60 to enable or increase flow of heat transfer fluid from the second stage 106 to the conduit 42. Upon a determination that the first mixing control valve 60 is in a fully open position to direct heat transfer fluid from the second stage 106 to the conduit 42, the control system 200 may gradually or incrementally adjust the fourth mixing control valve 66 to enable or increase flow of heat transfer fluid from the third stage 120 to the conduit 42. The control system 200 may execute the aforementioned adjustments until feedback from corresponding temperature sensors 426 indicates that the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 reaches (e.g., is within a threshold range of) the HT inlet set-point. Moreover, in some embodiments, the control system 200 may throttle (e.g., reduce) flow of relatively warm heat transfer fluid from the first stage 98 to the high temperature thermal loads 32 via adjustment of the first mixing control valve 60.

In some embodiments, upon a determination (e.g., based on feedback from the sixth supporting temperature sensor 418) that the first stage outlet temperature is less than the HT inlet set-point (e.g., by a threshold value), the control system 200 may operate the valve system 400 to increase a temperature of the heat transfer fluid received by the high temperature thermal loads 32 to cause the temperature of the heat transfer fluid received at the inlets 24 of the high temperature thermal loads 32 to approach the HT inlet set-point. For example, the control system 200 may evaluate feedback from one or more of the fourth temperature sensors 80 and/or from the fourteenth temperature sensor 450 to determine the LT-load outlet temperature. Upon a determination that the LT-load outlet temperature is greater than the HT inlet set-point, the control system 200 may modulate the second mixing control valve 62 to direct heat transfer fluid from the low temperature outlet conduit 428 into the conduit 42 and toward the high temperature thermal loads 32. To this end, the control system 200 may mix (e.g., in the conduit 42) heat transfer fluid received from the first stage 98 and heat transfer fluid received from the low temperature outlet conduit 428 to increase a temperature of the heat transfer fluid received at the high temperature thermal loads 32. The control system 200 may monitor a temperature of the mixed heat transfer fluid directed toward the high temperature thermal loads 32 via feedback received from the additional first supporting temperature sensor 414 to determine a difference between the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 and the HT inlet set-point.

Upon a determination that substantially all of the heat transfer fluid from the low temperature outlet conduit 428 is directed into the conduit 42 and to the high temperature thermal loads 32 (e.g., based on feedback from the flow sensor 432 indicating that there is substantially no fluid flow from the low temperature outlet conduit 428 to the distribution conduit 430), and that the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 is still below the HT inlet set-point, the control system 200 may modulate the third mixing control valve 64 to enable or increase flow of heat transfer fluid along a recirculation conduit 452 that enables flow of heated heat transfer fluid (e.g., return heat transfer fluid) from the return conduit 48 back to the conduit 42 and into the high temperature thermal loads 32. The control system 200 may gradually or incrementally adjust the third mixing control valve 64 to increase the flow of heat transfer fluid recirculated from the return conduit 48 to the high temperature thermal loads 32 until feedback from, for example, the first temperature sensor 40, indicates that the temperature of the mixed heat transfer fluid received at the high temperature thermal loads 32 is substantially equal to (e.g., within a threshold range of) the HT inlet set-point.

As discussed above, in some embodiments, the control system 200 may disregard the temperature of the heat transfer fluid supplied to the high temperature thermal loads 32 and may control the HVAC&R system 12 to cause a temperature of the heat transfer fluid discharged from each high temperature thermal load 32 to have a temperature that is substantially equal to the corresponding HT outlet set-point of the high temperature thermal load 32. Moreover, the control system 200 may disregard the temperature of the heat transfer fluid supplied to the low temperature thermal loads 30 and may control the HVAC&R system 12 to cause a temperature of the heat transfer fluid discharged from each low temperature thermal load 30 to have a temperature that is substantially equal to the corresponding LT outlet set-point of the low temperature thermal load 30. In accordance with the techniques discussed above, in such embodiments, the control system 200 may adjust an operating speed of the first pumps 52 (e.g., one or more pumps) and the second pumps 84 (e.g., one or more pumps) to adjust the temperature of heat transfer fluid discharging from the high temperature thermal loads 32 and the low temperature thermal loads 30, respectively.

For example, the control system 200 may receive feedback from one or more of the second temperature sensors 44 indicative of a temperature of the heat transfer fluid discharging from the high temperature thermal loads 32. In response to a determination that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is above the HT outlet set-point (e.g., by a threshold amount), the control system 200 may gradually or incrementally (e.g., after lapse of a time delay) increase a speed of the first pumps 52 to increase a flow rate of the heat transfer fluid directed through the high temperature thermal loads 32. In this manner, the control system 200 may effectuate a reduction in the temperature of heat transfer fluid discharging from the high temperature thermal loads 32 by distributing the thermal energy output by the high temperature thermal loads 32 to an increased quantity of the heat transfer fluid. The control system 200 may continue to increase the speed of the first pumps 52 until the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 approaches the HT outlet set-point (e.g., is within a threshold range of the HT outlet set-point) or until the first pumps 52 reach a threshold operating speed (e.g., an upper operating speed threshold).

In response to determining that the first pumps 52 reach the threshold operating speed, and that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is still above the HT outlet set-point (e.g., by a threshold amount), the control system 200 may determine (e.g., based on feedback from corresponding temperature sensors 426) whether the temperature of the heat transfer fluid in the low temperature outlet conduit 428 is less than the temperature of the heat transfer fluid measured by the additional first supporting temperature sensor 414. Upon a determination that the LT-load outlet temperature is less than the temperature of the heat transfer fluid measured by the additional first supporting temperature sensor 414, the control system 200 may modulate the second mixing control valve 62 in accordance with the techniques discussed above to direct heat transfer fluid from the low temperature outlet conduit 428 into the conduit 42 and toward the high temperature thermal loads 32. To this end, the control system 200 may mix (e.g., in the conduit 42) heat transfer fluid received from the first stage 98 and heat transfer fluid received from the low temperature outlet conduit 428 to reduce a temperature of the heat transfer fluid received at the high temperature thermal loads 32. The control system 200 may monitor a temperature of the mixed heat transfer fluid discharging from the high temperature thermal loads 32 (e.g., via feedback acquired by one or more of the second temperature sensors 44) to determine a difference between the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 and the HT outlet set-point.

The control system 200 may operate the second mixing control valve 62 to continue to increase the flow of heat transfer fluid from the low temperature outlet conduit 428 to the high temperature thermal loads 32 until the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 (e.g., as measured by the second temperature sensors 44) is substantially equal to (e.g., within a threshold range of) the HT outlet set-point or until the flow sensor 432 indicates that substantially no flow of heat transfer fluid is directed into the distribution conduit 430 as bypass flow. Upon a determination (e.g., based on feedback from the flow sensor 432) that the second mixing control valve 62 directs substantially all of the heat transfer fluid received from the low temperature outlet conduit 428 into the conduit 42 and toward the high temperature thermal loads 32, and that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is still above the HT outlet set-point, the control system 200 may operate the first mixing control valve 60 and/or the fourth mixing control valve 66 in accordance with the techniques discussed above to direct heat transfer fluid from the second stage 106 and/or the third stage 120 to the conduit 42 to provide additional cooled heat transfer fluid to the high temperature thermal loads 32.

In response to a determination that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is below the HT outlet set-point (e.g., by a threshold amount), the control system 200 may gradually or incrementally (e.g., after lapse of a time delay) decrease the speed of the first pumps 52 to reduce a flow rate of the heat transfer fluid directed through the high temperature thermal loads 32. In this manner, the control system 200 may effectuate an increase in the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 by distributing the thermal energy output by the high temperature thermal loads 32 to a reduced quantity of the heat transfer fluid. The control system 200 may continue to decrease the speed of the first pumps 52 until the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 approaches the HT outlet set-point or until the first pumps 52 reach a lower threshold operating speed.

In response to determining that the first pumps 52 reach the lower threshold operating speed, and that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is still below the HT outlet set-point, the control system 200 may determine (e.g., based on feedback from corresponding temperature sensors 426) whether the temperature of the heat transfer fluid in the low temperature outlet conduit 428 is greater than the temperature of the heat transfer fluid measured by the additional first supporting temperature sensor 414. Upon a determination that the LT-load outlet temperature is greater than the temperature of the heat transfer fluid measured by the additional first supporting temperature sensor 414, the control system 200 may modulate the second mixing control valve 62 in accordance with the techniques discussed above to direct heat transfer fluid from the low temperature outlet conduit 428 into the conduit 42 and toward the high temperature thermal loads 32. To this end, the control system 200 may mix (e.g., in the conduit 42) heat transfer fluid received from the first stage 98 and heat transfer fluid received from the low temperature outlet conduit 428 to increase a temperature of the heat transfer fluid received at the high temperature thermal loads 32. The control system 200 may monitor a temperature of the mixed heat transfer fluid discharging from the high temperature thermal loads 32 (e.g., via feedback acquired by one or more of the second temperature sensors 44) to determine a difference between the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 and the HT outlet set-point.

The control system 200 may operate the second mixing control valve 62 to continue to increase the flow of heat transfer fluid from the low temperature outlet conduit 428 to the high temperature thermal loads 32 until the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 (e.g., as measured by the second temperature sensors 44) is substantially equal to (e.g., within a threshold range of) the HT outlet set-point or until the flow sensor 432 indicates that substantially no flow of heat transfer fluid is directed into the distribution conduit 430 as bypass flow. Upon a determination (e.g., based on feedback from the flow sensor 432) that the second mixing control valve 62 directs substantially all of the heat transfer fluid received from the low temperature outlet conduit 428 into the conduit 42 and toward the high temperature thermal loads 32, and that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is still below the HT outlet set-point, the control system 200 may modulate the third mixing control valve 64 to enable or increase flow of heat transfer fluid from the recirculation conduit 452 to the inlets 24 of the high temperature thermal loads 32. The control system 200 may gradually or incrementally operate the third mixing control valve 64 to continue to increase the flow of heat transfer fluid from the recirculation conduit 452 to the high temperature thermal loads 32 until feedback from, for example, the second temperature sensors 44, indicate that the temperature of the heat transfer fluid discharging from the high temperature thermal loads 32 is substantially equal to (e.g., within a threshold range of) the HT outlet set-point.

In some embodiments, the distribution conduit 430 is configured to direct at least a portion of the heat transfer fluid (e.g., a bypass flow) received from the low temperature outlet conduit 428 back to the heat rejection components 22 without first directing the heat transfer fluid through the high temperature thermal loads 32. For example, as shown in the illustrated embodiment of FIG. 4, the distribution conduit 430 may be fluidly coupled to the first distribution valve 402, the second distribution valve 404, the third distribution valve 406, and the fourth distribution valve 408, which may be configured to regulate flow of heat transfer fluid from the distribution conduit 430 toward various of the heat rejection components 22. In some embodiments, the control system 200 may adjust the valve system 400 to direct heat transfer fluid from the low temperature outlet conduit 428 to particular locations in the fluid loop 18 based on a temperature of the heat transfer fluid in the low temperature outlet conduit 428. The control system 200 may adjust any of the first distribution valve 402, the second distribution valve 404, the third distribution valve 406, and/or the fourth distribution valve 408 upon receiving feedback from the flow sensor 432 that a non-zero amount of heat transfer fluid is bypassing the second mixing control valve 62 and is being directed into the distribution conduit 430. In particular, as discussed below, to enable flow of heat transfer fluid through the flow sensor 432 at a non-zero amount, the control system 200 may transition any one of the first distribution valve 402, the second distribution valve 404, the third distribution valve 406, or the fourth distribution valve 408 to an open position, while retaining the remaining distribution valves 410 in respective closed positions.

For example, the control system 200 may receive feedback from one or more of the fourth temperature sensors 80, and/or from the fourteenth temperature sensor 450 disposed along the low temperature outlet conduit 428, indicative of the temperature of the heat transfer fluid discharging from the low temperature thermal loads 30 and flowing within the low temperature outlet conduit 428. In response to a determination that the temperature of the heat transfer fluid in the low temperature outlet conduit 428 (e.g., a temperature of heated, return heat transfer fluid discharged from the low temperature thermal loads 30) is less than or equal to a temperature of the heat transfer fluid discharging from the second stage 106 (e.g., based on comparison to feedback from the seventh temperature sensor 144), the control system 200 may instruct the fourth distribution valve 408 to transition to an open position while instructing the first, second, and third distribution valves 402, 404, and 406 to transition to closed positions. As such, the control system 200 may direct heat transfer fluid bypassing the second modulating control valve 62 from the flow sensor 432 to the conduit 122 via the fourth distribution valve 408.

In response to a determination that the temperature of the heat transfer fluid in the low temperature outlet conduit 428 is greater than the temperature of the heat transfer fluid discharging from the second stage 106 but less than or equal to a temperature of the heat transfer fluid discharging from the first stage 98 (e.g., based on comparison to feedback from the sixth temperature sensor 142), the control system 200 may instruct the third distribution valve 406 to transition to an open position while instructing the first, second, and fourth distribution valves 402, 404, and 408 to transition to closed positions. As such, the control system 200 may direct heat transfer fluid (e.g., return heat transfer fluid) bypassing the second mixing control valve 62 from the flow sensor 432 to the conduit 108 via the third distribution valve 406. In response to a determination that the temperature of the heat transfer fluid in the low temperature outlet conduit 428 is greater than the temperature of the heat transfer fluid discharging from the first stage 98 but less than or equal to a temperature of the heat transfer fluid discharging from the base stage 92 (e.g., based on comparison to feedback from the fifth temperature sensor 140), the control system 200 may instruct the second distribution valve 404 to transition to an open position while instructing the first, third, and fourth distribution valves 402, 406, and 408 to transition to closed positions. As such, the control system 200 may direct any heat transfer fluid (e.g., return heat transfer fluid) bypassing the second mixing control valve 62 from the flow sensor 432 to the conduit 100 via the second distribution valve 404. Further, in response to a determination that the temperature of the heat transfer fluid in the low temperature outlet conduit 428 is greater than the temperature of the heat transfer fluid discharging from the base stage 92, the control system 200 may instruct the first distribution valve 402 to transition to an open position while instructing the second, third, and fourth distribution valves 404, 406, and 408 to transition to closed positions. As such, the control system 200 may direct any heat transfer fluid (e.g., return heat transfer fluid) bypassing the second mixing control valve 62 from the flow sensor 432 to the return conduit 48 via the first distribution valve 402. By controlling the first, second, third, and fourth distribution valves 402, 404, 406, and 408 in accordance with the aforementioned techniques, the control system 200 may increase the amount of heat recovery available to the heat recovery load 244 via the base stage 92 (e.g., via the heat recovery heat exchanger 96) and enhance an overall operational efficiency of the first stage 98, the second stage 106, and/or the third stage 120. In some embodiments, the control system 200 may be configured to periodically update the position of the distribution valves 410 (e.g., based on feedback) upon lapse of a predetermined time interval (e.g., 10 seconds).

As discussed above, in some embodiments, certain components of the multi-stage thermal management system 10 may be positioned on one or more skid assemblies. To better illustrate and to facilitate the following discussion, FIG. 5 is a schematic of an embodiment of the multi-stage thermal management system 10 illustrating a portion 500 of the multi-stage thermal management system 10 positioned on a skid assembly 502. Particularly, in the illustrated embodiment, at least a portion of the fluid loop 18 is positioned on (e.g., coupled to) the skid assembly 502. The skid assembly 502 includes a plurality of flanges 504 that facilitate fluid coupling of the portion of the fluid loop 18 disposed on the skid assembly 502 and components of the multi-stage thermal management system 10 that may not be supported by the skid assembly 502. For example, the fluid loop 18 may include a first set of flanges 504 that facilitate fluid coupling of the fluid loop 18 of the skid assembly 502 and the base stage 92, a second set of flanges 504 that facilitate fluid coupling of the fluid loop 18 of the skid assembly 502 and the first stage 98, a third set of flanges 504 that facilitate fluid coupling of the fluid loop 18 of the skid assembly 502 and the second stage 106, and so forth. Moreover, the skid assembly 502 may include flanges 504 that facilitate coupling of the thermal loads 14 to the fluid loop 18 on the skid assembly 502. In this manner, the base, first, second, and/or third stages 92, 98, 106, and/or 120 of the multi-stage thermal management system 10 may be positioned remotely from the skid assembly 502. As a non-limiting example, the skid assembly 502 may be positioned within an interior of a building or other structure, while any one or combination of the stages 90 may be positioned on a roof of the building, in a basement of the building, or at another suitable location. Moreover, the thermal loads 14 may be positioned remotely from the skid assembly 502.

In certain embodiments, the skid assembly 502 may be configured to enable implementation of embodiments of the disclosed multi-stage thermal management system 10 in various facilitates that include additional or fewer stages 90 than the stages 90 shown in the illustrated embodiment of FIG. 5. For example, in some embodiments, a particular facility may not include the first stage 98. In such embodiments, end caps (e.g., plugs) may be coupled to the flanges 504 associated with the first stage 98. Additionally or alternatively, valves of the skid assembly 502 associated with the first stage 98 may be transitioned to closed positions to block fluid flow to the flanges 504 associated with the first stage 98. In any case, the control system 200 may operate the multi-stage thermal management system 10 in accordance with the techniques discussed above, regardless of the particular stages 90 included in the multi-stage thermal management system 10. As such, it should be understood that the control system 200 may be configured to operate embodiments of the multi-stage thermal management system 10 having any suitable number and/or combination of stages 90. In certain embodiments, the fluid loop 18 on the skid assembly 502 may include valves 506 that are communicatively coupled to the control system 200. The control system 200 may be configured to actuate the valves 506 to enable flow of heat transfer fluid to one or more stages 90 or to enable heat transfer fluid in the fluid loop 18 to bypass one or more stages 90.

FIG. 6 is a schematic of an embodiment of the multi-stage thermal management system 10 including multiple skid assemblies 520. In particular, the multi-stage thermal management system 10 includes a first skid 522, a second skid 524, and a third skid 526. In the illustrated embodiment, the first skid 522 supports the chiller system 126, the second skid 524 supports the first and second pumps 52, 84, the mixing control valves 74, at least a portion of the distribution valves 410, and the first stage 98, and the third skid 526 supports the high temperature thermal loads 32 and the low temperature thermal loads 30 with associated modulating valves 50, 82. It should be appreciated that, in other embodiments, the multi-stage thermal management system 10 may include any other suitable quantity of skid assemblies 520. Moreover, each of the skid assemblies 520 may include additional components or fewer components of the multi-stage thermal management system 10 than those shown in the illustrated embodiment of FIG. 6.

As set forth above, embodiments of the present disclosure may provide one or more technical effects useful for enabling independent temperature regulation of one or more thermal loads of an HVAC&R system based on individual cooling demands of the thermal loads and in accordance with the target temperature set-points corresponding to the thermal loads. Further, embodiments of the present disclosure may provide one or more technical effects useful for coordinating operation of the heat exchange equipment of the HVAC&R system based on one or more monitored efficiency parameters to increase an overall operational efficiency of the HVAC&R system. The technical effects and technical problems in the specification are examples and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.

It should be understood that the application is not limited to the details or methodology set forth in the following description or illustrated in the figures. It should also be understood that the phraseology and terminology employed herein is for the purpose of description only and should not be regarded as limiting. The present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims. The order or sequence of any processes or method steps may be varied or re-sequenced according to alternative embodiments.

It is important to note that the construction and arrangement of the multi-stage thermal management system as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application.

The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f). 

1. A multi-stage thermal management system, comprising: a fluid loop configured to supply a chilled heat transfer fluid to a plurality of thermal loads having different cooling demands; a plurality of heat rejection components arranged in a plurality of stages, wherein the plurality of heat rejection components is fluidly coupled to the fluid loop, wherein the plurality of heat rejection components is configured to receive a return heat transfer fluid from the plurality of thermal loads and extract heat from the return heat transfer fluid to generate the chilled heat transfer fluid; and a control system configured to selectively draw the chilled heat transfer fluid from each heat rejection component of the plurality of heat rejection components individually and to direct the chilled heat transfer fluid to the plurality of thermal loads via the fluid loop based on the different cooling demands of the plurality of thermal loads to meet each of the different cooling demands via supply of the chilled heat transfer fluid.
 2. The multi-stage thermal management system of claim 1, wherein the plurality of thermal loads comprises one or more low temperature thermal loads having a first target temperature set-point and one or more high temperature thermal loads having a second target temperature set-point different than the first target temperature set-point.
 3. The multi-stage thermal management system of claim 2, comprising a plurality of valves fluidly coupled to the plurality of heat rejection components, the one or more low temperature thermal loads, and the one or more high temperature thermal loads, wherein the control system is configured to control the plurality of valves to selectively direct chilled heat transfer fluid discharged from a first heat rejection component of the plurality of heat rejection components associated with a first selected stage of the plurality of stages to a first heat exchanger of the one or more low temperature thermal loads based on the first target temperature set-point.
 4. The multi-stage thermal management system of claim 3, wherein the control system is configured to control the plurality of valves to selectively direct chilled heat transfer fluid discharged from a second heat rejection component of the plurality of heat rejection components associated with a second selected stage of the plurality of stages to a second heat exchanger of the one or more high temperature thermal loads based on the second target temperature set-point.
 5. The multi-stage thermal management system of claim 4, wherein the first heat exchanger of the one or more low temperature thermal loads is configured to reject heat to the chilled heat transfer fluid to generate the return heat transfer fluid, wherein the control system is configured to control the plurality of valves based on the second target temperature set-point of the one or more high temperature thermal loads to direct a portion of the return heat transfer fluid discharged from the first heat exchanger of the one or more low temperature thermal loads to the second heat exchanger of the one or more high temperature thermal loads.
 6. The multi-stage thermal management system of claim 1, wherein the control system is configured to selectively activate one or more heat rejection components of the plurality of heat rejection components based on one or more efficiency parameters.
 7. The multi-stage thermal management system of claim 6, wherein the one or more efficiency parameters comprise a cost of electrical energy, a cost of water, a temperature of ambient air surrounding the multi-stage thermal management system, a humidity level of the ambient air, or a combination thereof.
 8. The multi-stage thermal management system of claim 1, wherein the plurality of stages comprises: a base stage comprising a first heat rejection component of the plurality of heat rejection components; and a first stage comprising a second heat rejection component of the plurality of heat rejection components, and wherein the control system is configured to: operate the base stage without operating the first stage to supply the chilled heat transfer fluid to the plurality of thermal loads; and operate the base stage and the first stage based on a determination that the chilled heat transfer fluid discharged by the first heat rejection component does not satisfy the different cooling demands of the plurality of thermal loads.
 9. The multi-stage thermal management system of claim 1, comprising a plurality of skids, wherein one or more of the plurality of heat rejection components is mounted to a first skid of the plurality of skids and one or more of the plurality of thermal loads is mounted to a second skid of the plurality of skids.
 10. A multi-stage thermal management system, comprising: a fluid loop configured to supply a chilled heat transfer fluid to a plurality of thermal loads having different cooling demands, wherein each thermal load of the plurality of thermal loads comprises a respective heat exchanger configured to reject heat to the chilled heat transfer fluid to produce return heat transfer fluid; a plurality of heat rejection components arranged in a plurality of stages, wherein the plurality of heat rejection components is fluidly coupled to the fluid loop, wherein the plurality of heat rejection components is configured to extract thermal energy from the return heat transfer fluid to produce the chilled heat transfer fluid; and a control system configured to adjust a valve system of the fluid loop to selectively direct a portion of the return heat transfer fluid to a heat rejection component of the plurality of heat rejection components associated with a selected stage of the plurality of stages based on a return temperature of the portion of the return heat transfer fluid.
 11. The multi-stage thermal management system of claim 10, wherein the control system is configured to: receive, from a first sensor, data indicative of the return temperature; receive, from a second sensor, data indicative of a first temperature of chilled heat transfer fluid discharged from the heat rejection component associated with the selected stage of the plurality of stages via a conduit; and adjust the valve system to direct the portion of the return heat transfer fluid along the fluid loop and into the conduit in response to a determination that the return temperature is less than the first temperature.
 12. The multi-stage thermal management system of claim 11, wherein the control system is configured to: receive, from a third sensor, data indicative of a second temperature of chilled heat transfer fluid discharged from an additional heat rejection component of the plurality of heat rejection components associated with an additional stage of the plurality of stages and directed into the heat rejection component associated with the selected stage via an additional conduit; and adjust the valve system to direct the portion of the return heat transfer fluid along the fluid loop and into the additional conduit in response to a determination that the return temperature is greater than the first temperature and less than the second temperature.
 13. The multi-stage thermal management system of claim 10, wherein the plurality of thermal loads comprises: a low temperature thermal load having one or more first heat exchangers; and a high temperature thermal load having one or more second heat exchangers, wherein the control system is configured to adjust the valve system to: direct a first amount of return heat transfer fluid discharged from the one or more first heat exchangers along the fluid loop to the selected stage as the portion of the return heat transfer fluid; and direct a second amount of return heat transfer fluid discharged from the one or more first heat exchangers along the fluid loop to the one or more second heat exchangers.
 14. The multi-stage thermal management system of claim 13, wherein the control system is configured to adjust flow of the second amount of return heat transfer fluid to the one or more second heat exchangers based on the return temperature, an additional temperature of mixed heat transfer fluid directed toward the one or more second heat exchangers, and a target temperature set-point of the one or more second heat exchangers.
 15. The multi-stage thermal management system of claim 10, wherein the control system is configured to selectively activate at least one heat rejection component of one or more stages of the plurality of stages based on the different cooling demands of the plurality of thermal loads, wherein the one or more stages comprise the selected stage.
 16. A multi-stage thermal management system, comprising: a fluid loop configured to supply chilled heat transfer fluid to a plurality of heat exchangers, wherein the plurality of heat exchangers is configured to reject heat to the chilled heat transfer fluid to produce and discharge a return heat transfer fluid; a plurality of stages of heat rejection components fluidly coupled to the fluid loop, wherein the plurality of stages of heat rejection components is configured to extract thermal energy from the return heat transfer fluid to generate the chilled heat transfer fluid; and a control system configured to adjust a valve system of the fluid loop to selectively direct a portion of the return heat transfer fluid to a selected stage of the plurality of stages of heat rejection components based on a return temperature of the portion of the return heat transfer fluid and respective temperatures of chilled heat transfer fluid discharged from the plurality of stages of heat rejection components.
 17. The multi-stage thermal management system of claim 16, wherein the plurality of stages of heat rejection components comprises: a base stage configured to receive a first flow of return heat transfer fluid from the plurality of heat exchangers and to discharge a second flow of chilled heat transfer fluid; and a first stage configured to receive the second flow of chilled heat transfer fluid, wherein the control system is configured to adjust the valve system to mix the portion of the return heat transfer fluid with the first flow of return heat transfer fluid in response to a determination that the return temperature exceeds a corresponding temperature of the second flow of chilled heat transfer fluid.
 18. The multi-stage thermal management system of claim 17, wherein the control system is configured to adjust the valve system to mix the portion of the return heat transfer fluid with the second flow of chilled heat transfer fluid in response to a determination that the return temperature is less than or equal to the corresponding temperature of the second flow of chilled heat transfer fluid.
 19. The multi-stage thermal management system of claim 16, wherein plurality of stages of heat rejection components comprises a heat recovery heat exchanger, a dry economizer, a wet economizer, and a chiller system.
 20. The multi-stage thermal management system of claim 19, wherein, in response to a determination that the heat recovery heat exchanger does not satisfy a cooling demand of the plurality of thermal loads, the control system is configured to activate one or more of the dry economizer, the wet economizer, and the chiller system based on one or more efficiency parameters of the multi-stage thermal management system to generate the chilled heat transfer fluid. 